diff --git a/assets/icons/ui/source/glyphs.rs b/assets/icons/ui/source/glyphs.rs
index 828e8e34..c2b5eba7 100644
--- a/assets/icons/ui/source/glyphs.rs
+++ b/assets/icons/ui/source/glyphs.rs
@@ -100,7 +100,7 @@ pub(crate) fn brand_mark(p: &egui::Painter, c: Pos2) {
     let face = |col: Color32, pts: &[(f32, f32)]| {
         p.add(egui::Shape::convex_polygon(m(pts), col, Stroke::NONE));
     };
-    let (light, mid, dark) = (Color32::from_rgb(96, 158, 236), Color32::from_rgb(58, 136, 238), Color32::from_rgb(55, 108, 197));
+    let [light, mid, dark, edge_col] = crate::theme::Tokens::get().logo;
     face(light, &[(3.5, 105.9), (177.0, 5.8), (263.4, 55.6), (263.8, 156.0), (177.0, 406.4)]);
     face(light, &[(177.0, 206.1), (263.8, 156.0), (350.5, 206.2), (350.5, 306.3), (177.0, 406.4)]);
     face(mid, &[(3.5, 105.9), (177.0, 206.1), (177.0, 406.4)]);
@@ -111,7 +111,7 @@ pub(crate) fn brand_mark(p: &egui::Painter, c: Pos2) {
     face(dark, &[(177.0, 206.1), (177.0, 406.4), (350.5, 306.3)]);
     face(dark, &[(263.8, 55.9), (263.8, 156.0), (177.1, 105.9)]);
     // White edge lines.
-    let edge = Stroke::new(10.0 * s, Color32::WHITE);
+    let edge = Stroke::new(10.0 * s, edge_col);
     let line = |pts: &[(f32, f32)]| {
         p.add(egui::Shape::line(m(pts), edge));
     };
diff --git a/assets/icons/ui/source/icons.rs b/assets/icons/ui/source/icons.rs
index 25df0e9d..f82c9c5d 100644
--- a/assets/icons/ui/source/icons.rs
+++ b/assets/icons/ui/source/icons.rs
@@ -3,13 +3,6 @@
 
 use egui::{Color32, Mesh, Painter, Pos2, Rect, Shape, Stroke, pos2, vec2};
 
-/// Surface sheets: a sheet, a second sheet beside it, a lighter sheet (an opening, a blend or
-/// round strip), and the iso lines and comb teeth drawn on sheets.
-const SHEET: Color32 = Color32::from_rgb(170, 200, 240);
-const SHEET_2: Color32 = Color32::from_rgb(150, 185, 235);
-const SHEET_LIGHT: Color32 = Color32::from_rgb(214, 229, 248);
-const SHEET_LINE: Color32 = Color32::from_rgb(127, 166, 218);
-
 /// `n + 1` points along the cubic Bézier curve with control points `c`.
 fn bezier(c: [(f32, f32); 4], n: usize) -> Vec<(f32, f32)> {
     (0..=n)
@@ -127,6 +120,12 @@ fn line_type_dot_radius(r: Rect) -> f32 {
 
 /// Paint the icon `name` into `r`. `accent` highlights the "action" part.
 pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, accent: Color32) {
+    paint_with(p, r, name, ink, fill, accent, &crate::theme::Tokens::get().icons);
+}
+
+/// [`paint`] with the colours an icon draws of its own given (`theme::IconColors`).
+pub(crate) fn paint_with(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, accent: Color32, ic: &crate::theme::IconColors) {
+    let ic = *ic;
     let pen = Pen { p, r, ink, fill, accent, w: (r.width() / 24.0 * 1.4).max(1.0) };
     let a = pen.accent;
     match name {
@@ -164,7 +163,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         "sphere" => {
             pen.circle(12.0, 12.0, 8.5, pen.fill, ink);
             pen.arc(12.0, 12.0, 8.5, 3.3, 6.1, ink.gamma_multiply(0.5));
-            p.circle_filled(pen.at(9.0, 8.5), 2.0 * pen.s(), Color32::from_white_alpha(160));
+            p.circle_filled(pen.at(9.0, 8.5), 2.0 * pen.s(), ic.glint);
         }
         "torus" => {
             let pts: Vec<Pos2> =
@@ -172,7 +171,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             p.add(Shape::convex_polygon(pts, pen.fill, Stroke::new(pen.w, ink)));
             let pts: Vec<Pos2> =
                 (0..40).map(|i| i as f32 / 40.0 * std::f32::consts::TAU).map(|t| pen.at(12.0 + 3.5 * t.cos(), 11.0 + 1.8 * t.sin())).collect();
-            p.add(Shape::convex_polygon(pts, Color32::WHITE, Stroke::new(pen.w, ink)));
+            p.add(Shape::convex_polygon(pts, ic.highlight, Stroke::new(pen.w, ink)));
         }
         "fillet" => {
             pen.poly(&[(4.0, 20.0), (4.0, 4.0), (10.0, 4.0), (10.0, 14.0), (20.0, 14.0), (20.0, 20.0)], pen.fill, Color32::TRANSPARENT);
@@ -214,7 +213,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             pen.poly(&[(3.0, 8.0), (21.0, 8.0), (21.0, 20.0), (3.0, 20.0)], pen.fill, ink);
             let pts: Vec<Pos2> =
                 (0..32).map(|i| i as f32 / 32.0 * std::f32::consts::TAU).map(|t| pen.at(12.0 + 5.0 * t.cos(), 8.0 + 2.0 * t.sin())).collect();
-            p.add(Shape::convex_polygon(pts, Color32::WHITE, Stroke::new(pen.w, a)));
+            p.add(Shape::convex_polygon(pts, ic.highlight, Stroke::new(pen.w, a)));
             pen.line(&[(7.0, 8.0), (7.0, 16.0)], a);
             pen.line(&[(17.0, 8.0), (17.0, 16.0)], a);
         }
@@ -231,7 +230,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         }
         "shell" => {
             pen.iso_box(3.0, 9.0, 10.0, 8.0, 9.0);
-            pen.poly(&[(6.0, 9.0), (13.0, 5.5), (18.0, 8.0), (11.0, 11.5)], Color32::WHITE, a);
+            pen.poly(&[(6.0, 9.0), (13.0, 5.5), (18.0, 8.0), (11.0, 11.5)], ic.highlight, a);
         }
         "draft" => {
             pen.poly(&[(4.0, 20.0), (20.0, 20.0), (17.0, 5.0), (7.0, 5.0)], pen.fill, ink);
@@ -478,7 +477,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         "c_coincident" => {
             pen.line(&[(3.0, 18.0), (12.0, 12.0)], ink);
             pen.line(&[(12.0, 12.0), (21.0, 16.0)], ink);
-            pen.circle(12.0, 12.0, 2.6, Color32::WHITE, a);
+            pen.circle(12.0, 12.0, 2.6, ic.highlight, a);
         }
         "c_tangent" => {
             pen.circle(12.0, 14.0, 6.0, Color32::TRANSPARENT, ink);
@@ -525,7 +524,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             pen.arrow((x1 + (x0 - x1) * 0.15, 9.0), (x1, 9.0), ink);
         }
         "new" => {
-            pen.poly(&[(6.0, 3.0), (15.0, 3.0), (19.0, 7.0), (19.0, 21.0), (6.0, 21.0)], Color32::WHITE, ink);
+            pen.poly(&[(6.0, 3.0), (15.0, 3.0), (19.0, 7.0), (19.0, 21.0), (6.0, 21.0)], ic.highlight, ink);
             pen.line(&[(15.0, 3.0), (15.0, 7.0), (19.0, 7.0)], ink);
         }
         "open" => {
@@ -533,7 +532,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         }
         "save" => {
             pen.poly(&[(4.0, 4.0), (17.0, 4.0), (20.0, 7.0), (20.0, 20.0), (4.0, 20.0)], pen.fill, ink);
-            pen.poly(&[(8.0, 4.0), (16.0, 4.0), (16.0, 9.0), (8.0, 9.0)], Color32::WHITE, ink);
+            pen.poly(&[(8.0, 4.0), (16.0, 4.0), (16.0, 9.0), (8.0, 9.0)], ic.highlight, ink);
         }
         "export" => {
             pen.poly(&[(4.0, 10.0), (4.0, 20.0), (16.0, 20.0), (16.0, 10.0)], pen.fill, ink);
@@ -572,7 +571,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             }
         }
         "zoom" => {
-            pen.circle(10.0, 10.0, 6.0, Color32::WHITE, ink);
+            pen.circle(10.0, 10.0, 6.0, ic.highlight, ink);
             pen.line(&[(14.5, 14.5), (20.0, 20.0)], ink);
         }
         "perspective" => {
@@ -590,13 +589,13 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             pen.iso_box(2.0, 13.0, 9.0, 6.0, 6.0);
             pen.iso_box(9.0, 6.0, 5.0, 4.0, 4.0);
         }
-        "folder" => pen.poly(&[(3.0, 7.0), (9.0, 7.0), (11.0, 9.0), (21.0, 9.0), (21.0, 19.0), (3.0, 19.0)], Color32::from_rgb(236, 200, 110), ink),
+        "folder" => pen.poly(&[(3.0, 7.0), (9.0, 7.0), (11.0, 9.0), (21.0, 9.0), (21.0, 19.0), (3.0, 19.0)], ic.folder, ink),
         "origin" => {
-            pen.arrow((6.0, 18.0), (20.0, 18.0), Color32::from_rgb(210, 60, 60));
-            pen.arrow((6.0, 18.0), (6.0, 4.0), Color32::from_rgb(60, 100, 220));
-            pen.arrow((6.0, 18.0), (15.0, 9.0), Color32::from_rgb(60, 160, 60));
+            pen.arrow((6.0, 18.0), (20.0, 18.0), ic.axes[0]);
+            pen.arrow((6.0, 18.0), (6.0, 4.0), ic.axes[2]);
+            pen.arrow((6.0, 18.0), (15.0, 9.0), ic.axes[1]);
         }
-        "plane" => pen.poly(&[(3.0, 15.0), (12.0, 8.0), (21.0, 11.0), (12.0, 18.0)], Color32::from_rgb(244, 214, 150), ink),
+        "plane" => pen.poly(&[(3.0, 15.0), (12.0, 8.0), (21.0, 11.0), (12.0, 18.0)], ic.plane, ink),
         "axis" => {
             pen.line(&[(4.0, 20.0), (20.0, 4.0)], ink);
             pen.circle(4.0, 20.0, 2.0, ink, ink);
@@ -825,8 +824,8 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             }
         }
         "accessibility" => {
-            pen.poly(&[(2.0, 20.0), (22.0, 20.0), (22.0, 15.0), (2.0, 15.0)], Color32::from_rgb(70, 180, 90), ink);
-            pen.poly(&[(8.0, 15.0), (16.0, 15.0), (16.0, 17.5), (8.0, 17.5)], Color32::from_rgb(220, 70, 60), Color32::TRANSPARENT);
+            pen.poly(&[(2.0, 20.0), (22.0, 20.0), (22.0, 15.0), (2.0, 15.0)], ic.access[0], ink);
+            pen.poly(&[(8.0, 15.0), (16.0, 15.0), (16.0, 17.5), (8.0, 17.5)], ic.access[1], Color32::TRANSPARENT);
             pen.poly(&[(6.0, 10.0), (18.0, 10.0), (18.0, 12.5), (6.0, 12.5)], pen.fill, ink);
             pen.arrow((4.0, 2.0), (4.0, 13.0), a);
             pen.arrow((20.0, 2.0), (20.0, 13.0), a);
@@ -834,10 +833,10 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         "environment_map" => {
             let pts: Vec<Pos2> =
                 (0..32).map(|i| i as f32 / 32.0 * std::f32::consts::TAU).map(|t| pen.at(12.0 + 9.0 * t.cos(), 12.0 + 9.0 * t.sin())).collect();
-            p.add(Shape::convex_polygon(pts, Color32::from_rgb(190, 205, 230), Stroke::new(pen.w, ink)));
-            pen.poly(&[(3.6, 13.0), (20.4, 13.0), (18.5, 17.5), (5.5, 17.5)], Color32::from_rgb(60, 62, 70), Color32::TRANSPARENT);
-            pen.line(&[(3.2, 12.6), (20.8, 12.6)], Color32::WHITE);
-            p.circle_filled(pen.at(9.0, 8.0), 2.2 * pen.s(), Color32::WHITE);
+            p.add(Shape::convex_polygon(pts, ic.sky, Stroke::new(pen.w, ink)));
+            pen.poly(&[(3.6, 13.0), (20.4, 13.0), (18.5, 17.5), (5.5, 17.5)], ic.floor, Color32::TRANSPARENT);
+            pen.line(&[(3.2, 12.6), (20.8, 12.6)], ic.highlight);
+            p.circle_filled(pen.at(9.0, 8.0), 2.2 * pen.s(), ic.highlight);
             pen.circle(12.0, 12.0, 9.0, Color32::TRANSPARENT, ink);
         }
         "zebra" | "draft_analysis" | "curvature_map" => {
@@ -845,27 +844,23 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
                 (0..32).map(|i| i as f32 / 32.0 * std::f32::consts::TAU).map(|t| pen.at(12.0 + 9.0 * t.cos(), 12.0 + 9.0 * t.sin())).collect();
             match name {
                 "zebra" => {
-                    p.add(Shape::convex_polygon(pts, Color32::WHITE, Stroke::new(pen.w, ink)));
+                    p.add(Shape::convex_polygon(pts, ic.highlight, Stroke::new(pen.w, ink)));
                     for k in 0..3 {
                         let y = 6.5 + k as f32 * 4.5;
                         let h = (81.0 - (y + 1.0 - 12.0) * (y + 1.0 - 12.0)).max(0.0).sqrt();
-                        pen.poly(
-                            &[(12.0 - h, y), (12.0 + h, y), (12.0 + h, y + 2.2), (12.0 - h, y + 2.2)],
-                            Color32::from_gray(30),
-                            Color32::TRANSPARENT,
-                        );
+                        pen.poly(&[(12.0 - h, y), (12.0 + h, y), (12.0 + h, y + 2.2), (12.0 - h, y + 2.2)], ic.stripe, Color32::TRANSPARENT);
                     }
                     pen.circle(12.0, 12.0, 9.0, Color32::TRANSPARENT, ink);
                 }
                 "draft_analysis" => {
-                    pen.poly(&[(4.0, 20.0), (20.0, 20.0), (17.0, 5.0), (7.0, 5.0)], Color32::from_rgb(70, 180, 90), ink);
-                    pen.poly(&[(7.0, 5.0), (17.0, 5.0), (16.0, 9.0), (8.0, 9.0)], Color32::from_rgb(235, 200, 50), Color32::TRANSPARENT);
+                    pen.poly(&[(4.0, 20.0), (20.0, 20.0), (17.0, 5.0), (7.0, 5.0)], ic.draft[0], ink);
+                    pen.poly(&[(7.0, 5.0), (17.0, 5.0), (16.0, 9.0), (8.0, 9.0)], ic.draft[1], Color32::TRANSPARENT);
                     pen.arrow((12.0, 16.0), (12.0, 1.5), a);
                 }
                 _ => {
-                    p.add(Shape::convex_polygon(pts, Color32::from_rgb(60, 110, 230), Stroke::new(pen.w, ink)));
-                    pen.circle(14.0, 10.0, 5.0, Color32::from_rgb(70, 190, 90), Color32::TRANSPARENT);
-                    pen.circle(15.5, 8.5, 2.2, Color32::from_rgb(225, 60, 45), Color32::TRANSPARENT);
+                    p.add(Shape::convex_polygon(pts, ic.curvature[0], Stroke::new(pen.w, ink)));
+                    pen.circle(14.0, 10.0, 5.0, ic.curvature[1], Color32::TRANSPARENT);
+                    pen.circle(15.5, 8.5, 2.2, ic.curvature[2], Color32::TRANSPARENT);
                 }
             }
         }
@@ -983,13 +978,13 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         }
         "patch" => {
             // A wire loop with a surface spanned across it.
-            pen.poly(&[(4.0, 16.0), (9.0, 6.0), (19.0, 5.0), (20.0, 15.0), (12.0, 20.0)], SHEET, ink);
+            pen.poly(&[(4.0, 16.0), (9.0, 6.0), (19.0, 5.0), (20.0, 15.0), (12.0, 20.0)], ic.sheet, ink);
             pen.line(&[(4.0, 16.0), (9.0, 6.0), (19.0, 5.0), (20.0, 15.0), (12.0, 20.0), (4.0, 16.0)], a);
         }
         "stitch" => {
             // Two surface patches sewn along their shared edge.
-            pen.poly(&[(3.0, 18.0), (11.0, 14.0), (11.0, 4.0), (3.0, 8.0)], SHEET, ink);
-            pen.poly(&[(13.0, 14.0), (21.0, 18.0), (21.0, 8.0), (13.0, 4.0)], SHEET_2, ink);
+            pen.poly(&[(3.0, 18.0), (11.0, 14.0), (11.0, 4.0), (3.0, 8.0)], ic.sheet, ink);
+            pen.poly(&[(13.0, 14.0), (21.0, 18.0), (21.0, 8.0), (13.0, 4.0)], ic.sheet_2, ink);
             for y in [6.0, 9.0, 12.0] {
                 pen.line(&[(10.0, y), (14.0, y + 1.5)], a);
             }
@@ -999,7 +994,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             let f = [(2.0, 12.5), (7.0, 9.5), (12.0, 15.5), (17.0, 12.5)];
             let b = [(6.4, 8.9), (11.4, 5.9), (16.4, 11.9), (21.4, 8.9)];
             let d = f.map(|(x, y)| (x, y + 6.0));
-            pen.band(&bezier(b, 16), &bezier(f, 16), SHEET);
+            pen.band(&bezier(b, 16), &bezier(f, 16), ic.sheet);
             pen.band(&bezier(f, 16), &bezier(d, 16), pen.fill.gamma_multiply(0.85));
             pen.poly(&[(17.0, 12.5), (21.4, 8.9), (21.4, 14.9), (17.0, 18.5)], pen.fill.gamma_multiply(0.7), ink);
             pen.line(&[(2.0, 12.5), (2.0, 18.5)], ink);
@@ -1042,7 +1037,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             // An open profile (accent) pulled up into a sheet.
             let top = [(4.0, 11.0), (8.0, 8.0), (13.0, 14.0), (20.0, 10.0)];
             let bottom = [(4.0, 20.0), (8.0, 17.0), (13.0, 23.0), (20.0, 19.0)];
-            pen.band(&bezier(top, 16), &bezier(bottom, 16), SHEET);
+            pen.band(&bezier(top, 16), &bezier(bottom, 16), ic.sheet);
             pen.line(&[(4.0, 11.0), (4.0, 20.0)], ink);
             pen.line(&[(20.0, 10.0), (20.0, 19.0)], ink);
             pen.curve(top, ink);
@@ -1053,13 +1048,13 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             // An open profile (accent) turned about the axis into a hollow band.
             let left = [(5.0, 6.0), (7.0, 10.0), (5.0, 14.0), (6.0, 18.0)];
             let right = [(19.0, 6.0), (17.0, 10.0), (19.0, 14.0), (18.0, 18.0)];
-            pen.band(&bezier(left, 16), &bezier(right, 16), SHEET);
+            pen.band(&bezier(left, 16), &bezier(right, 16), ic.sheet);
             let front = ellipse(12.0, 18.0, 6.0, 2.2, 0.0, std::f32::consts::PI, 16);
-            pen.poly(&front, SHEET, Color32::TRANSPARENT);
+            pen.poly(&front, ic.sheet, Color32::TRANSPARENT);
             // A closed fill takes each point once: a repeated end point spikes `poly`'s edge.
             let mut opening = ellipse(12.0, 6.0, 7.0, 2.2, 0.0, std::f32::consts::TAU, 32);
             opening.pop();
-            pen.poly(&opening, SHEET_LIGHT, ink);
+            pen.poly(&opening, ic.sheet_light, ink);
             pen.line(&front, ink);
             pen.curve(left, ink);
             pen.line(&[(12.0, 1.5), (12.0, 3.8)], ink);
@@ -1070,7 +1065,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             // A straight profile (accent) carried along a curved path: a ribbon.
             let near = [(4.0, 13.0), (8.0, 5.0), (14.0, 5.0), (20.0, 9.0)];
             let far = [(4.0, 20.0), (8.0, 12.0), (14.0, 12.0), (20.0, 16.0)];
-            pen.band(&bezier(near, 16), &bezier(far, 16), SHEET);
+            pen.band(&bezier(near, 16), &bezier(far, 16), ic.sheet);
             pen.curve(near, ink);
             pen.curve(far, ink);
             pen.line(&[(4.0, 13.0), (4.0, 20.0)], a);
@@ -1080,7 +1075,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             // Two open sections (accent) joined by a sheet.
             let top = [(5.0, 6.0), (9.0, 3.0), (14.0, 8.0), (19.0, 5.0)];
             let bottom = [(3.0, 19.0), (8.0, 15.0), (14.0, 22.0), (21.0, 18.0)];
-            pen.band(&bezier(top, 16), &bezier(bottom, 16), SHEET);
+            pen.band(&bezier(top, 16), &bezier(bottom, 16), ic.sheet);
             pen.line(&[(5.0, 6.0), (3.0, 19.0)], ink);
             pen.line(&[(19.0, 5.0), (21.0, 18.0)], ink);
             pen.curve(top, a);
@@ -1090,7 +1085,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             // A wavy sheet and its offset copy (dashed), the distance shown by the arrow.
             let back = [(6.0, 14.0), (10.0, 11.0), (15.0, 17.0), (21.0, 14.0)];
             let front = [(3.0, 20.0), (7.0, 17.0), (12.0, 23.0), (18.0, 20.0)];
-            pen.band(&bezier(back, 16), &bezier(front, 16), SHEET);
+            pen.band(&bezier(back, 16), &bezier(front, 16), ic.sheet);
             pen.curve(back, ink);
             pen.curve(front, ink);
             pen.line(&[(6.0, 14.0), (3.0, 20.0)], ink);
@@ -1104,7 +1099,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         "ruled" => {
             // A strip hanging off a block's edge (accent), ruled by straight lines.
             pen.poly(&[(2.0, 12.0), (12.0, 12.0), (12.0, 22.0), (2.0, 22.0)], pen.fill, ink);
-            pen.poly(&[(12.0, 12.0), (21.0, 4.0), (21.0, 14.0), (12.0, 22.0)], SHEET, ink);
+            pen.poly(&[(12.0, 12.0), (21.0, 4.0), (21.0, 14.0), (12.0, 22.0)], ic.sheet, ink);
             pen.line(&[(15.0, 9.3), (15.0, 19.3)], a);
             pen.line(&[(18.0, 6.7), (18.0, 16.7)], a);
             pen.line(&[(12.0, 12.0), (12.0, 22.0)], a);
@@ -1140,13 +1135,13 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
                 })
                 .collect();
             for (lo, hi) in rows.iter().zip(rows.iter().skip(1)) {
-                pen.band(lo, hi, SHEET);
+                pen.band(lo, hi, ic.sheet);
             }
             for j in [n / 3, 2 * n / 3] {
                 if let Some(r) = rows.get(j) {
-                    pen.line(r, SHEET_LINE);
+                    pen.line(r, ic.sheet_line);
                 }
-                pen.line(&rows.iter().filter_map(|r| r.get(j).copied()).collect::<Vec<_>>(), SHEET_LINE);
+                pen.line(&rows.iter().filter_map(|r| r.get(j).copied()).collect::<Vec<_>>(), ic.sheet_line);
             }
             for c in [left, top, right, bottom] {
                 pen.curve(c, a);
@@ -1160,29 +1155,29 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             // leaves both edges tangent.
             let near = [(13.0, 20.0), (8.5, 20.0), (10.5, 11.0), (6.0, 11.0)];
             let far = near.map(|(x, y)| (x + 4.4, y - 3.6));
-            pen.poly(&[(2.0, 11.0), (6.0, 11.0), (10.4, 7.4), (6.4, 7.4)], SHEET, ink);
-            pen.band(&bezier(near, 16), &bezier(far, 16), SHEET_LIGHT);
+            pen.poly(&[(2.0, 11.0), (6.0, 11.0), (10.4, 7.4), (6.4, 7.4)], ic.sheet, ink);
+            pen.band(&bezier(near, 16), &bezier(far, 16), ic.sheet_light);
             pen.curve(far, a);
-            pen.poly(&[(13.0, 20.0), (17.0, 20.0), (21.4, 16.4), (17.4, 16.4)], SHEET, ink);
+            pen.poly(&[(13.0, 20.0), (17.0, 20.0), (21.4, 16.4), (17.4, 16.4)], ic.sheet, ink);
             pen.curve(near, a);
         }
         "untrim" => {
             // A trimmed sheet whose hole (dashed, accent) is filled back in.
-            pen.poly(&[(3.0, 17.0), (9.0, 5.0), (21.0, 7.0), (16.0, 20.0)], SHEET, ink);
+            pen.poly(&[(3.0, 17.0), (9.0, 5.0), (21.0, 7.0), (16.0, 20.0)], ic.sheet, ink);
             let hole = ellipse(12.2, 12.3, 4.2, 3.2, 0.0, std::f32::consts::TAU, 32);
-            pen.poly(hole.get(1..).unwrap_or_default(), SHEET_LIGHT, Color32::TRANSPARENT);
+            pen.poly(hole.get(1..).unwrap_or_default(), ic.sheet_light, Color32::TRANSPARENT);
             pen.dashed(&hole, a);
         }
         "unstitch" => {
             // Two sheets pulled apart from their shared edge.
-            pen.poly(&[(2.0, 18.0), (9.0, 14.0), (9.0, 4.0), (2.0, 8.0)], SHEET, ink);
-            pen.poly(&[(15.0, 14.0), (22.0, 18.0), (22.0, 8.0), (15.0, 4.0)], SHEET_2, ink);
+            pen.poly(&[(2.0, 18.0), (9.0, 14.0), (9.0, 4.0), (2.0, 8.0)], ic.sheet, ink);
+            pen.poly(&[(15.0, 14.0), (22.0, 18.0), (22.0, 8.0), (15.0, 4.0)], ic.sheet_2, ink);
             pen.arrow((10.8, 11.0), (7.0, 11.0), a);
             pen.arrow((13.2, 11.0), (17.0, 11.0), a);
         }
         "reverse_normal" => {
             // A sheet with its old normal (faded) and the flipped one (accent).
-            pen.poly(&[(2.0, 14.0), (14.0, 10.0), (22.0, 13.0), (10.0, 18.0)], SHEET, ink);
+            pen.poly(&[(2.0, 14.0), (14.0, 10.0), (22.0, 13.0), (10.0, 18.0)], ic.sheet, ink);
             pen.arrow((12.0, 14.0), (12.0, 3.5), ink.gamma_multiply(0.5));
             pen.arrow((12.0, 14.0), (12.0, 22.5), a);
         }
@@ -1190,10 +1185,10 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
             // A wall sheet and a floor sheet joined by a round strip (accent edges).
             let near = [(3.0, 16.0), (3.0, 18.8), (5.2, 21.0), (8.0, 21.0)];
             let far = near.map(|(x, y)| (x + 4.4, y - 3.6));
-            pen.poly(&[(3.0, 16.0), (3.0, 8.0), (7.4, 4.4), (7.4, 12.4)], SHEET_2, ink);
-            pen.poly(&[(8.0, 21.0), (16.0, 21.0), (20.4, 17.4), (12.4, 17.4)], SHEET, ink);
-            pen.band(&bezier(near, 16), &bezier(far, 16), SHEET_LIGHT);
-            pen.line(&[(4.5, 19.5), (8.9, 15.9)], SHEET_LINE);
+            pen.poly(&[(3.0, 16.0), (3.0, 8.0), (7.4, 4.4), (7.4, 12.4)], ic.sheet_2, ink);
+            pen.poly(&[(8.0, 21.0), (16.0, 21.0), (20.4, 17.4), (12.4, 17.4)], ic.sheet, ink);
+            pen.band(&bezier(near, 16), &bezier(far, 16), ic.sheet_light);
+            pen.line(&[(4.5, 19.5), (8.9, 15.9)], ic.sheet_line);
             pen.curve(far, a);
             pen.curve(near, a);
         }
@@ -1209,11 +1204,11 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
                 let h = 0.8 + 4.2 * i as f32 / 10.0;
                 let tip = (x + (y1 - y) / len * h, y - (x1 - x) / len * h);
                 if i % 2 == 0 {
-                    pen.line(&[(*x, *y), tip], SHEET_LINE);
+                    pen.line(&[(*x, *y), tip], ic.sheet_line);
                 }
                 tips.push(tip);
             }
-            pen.line(&tips, SHEET_LINE);
+            pen.line(&tips, ic.sheet_line);
             pen.curve(c, a);
             pen.dot(12.0, 13.0, a);
         }
@@ -1256,7 +1251,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         }
         "interference" => {
             pen.closed(&[(3.0, 5.0), (14.0, 5.0), (14.0, 16.0), (3.0, 16.0)], ink);
-            pen.poly(&[(9.0, 10.0), (14.0, 10.0), (14.0, 16.0), (9.0, 16.0)], Color32::from_rgb(225, 70, 60), Color32::from_rgb(225, 70, 60));
+            pen.poly(&[(9.0, 10.0), (14.0, 10.0), (14.0, 16.0), (9.0, 16.0)], ic.interference, ic.interference);
             pen.closed(&[(9.0, 10.0), (21.0, 10.0), (21.0, 20.0), (9.0, 20.0)], ink);
         }
         // Sheet metal: thin plates (fill), the made or changed part in the accent.
@@ -1283,7 +1278,7 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         "fold" => {
             pen.line(&[(2.0, 18.0), (12.0, 18.0)], ink);
             pen.line(&[(12.0, 18.0), (19.0, 6.0)], a);
-            pen.line(&[(9.0, 21.0), (15.0, 15.0)], Color32::from_rgb(130, 140, 160));
+            pen.line(&[(9.0, 21.0), (15.0, 15.0)], ic.fold);
             pen.arc(12.0, 18.0, 6.0, 0.2, 1.0, a);
             pen.arrow((18.0, 16.0), (17.0, 12.5), a);
         }
@@ -1358,13 +1353,13 @@ pub fn paint(p: &Painter, r: Rect, name: &str, ink: Color32, fill: Color32, acce
         // Appearance: a shaded ball with three paint dabs.
         "appearance" => {
             pen.circle(10.0, 13.0, 7.5, pen.fill, ink);
-            pen.arc(10.0, 13.0, 4.5, 1.8, 3.2, Color32::WHITE);
-            pen.circle(18.0, 5.0, 2.6, Color32::from_rgb(220, 70, 60), ink);
-            pen.circle(20.5, 11.0, 2.6, Color32::from_rgb(70, 150, 230), ink);
-            pen.circle(19.0, 17.5, 2.6, Color32::from_rgb(240, 200, 60), ink);
+            pen.arc(10.0, 13.0, 4.5, 1.8, 3.2, ic.highlight);
+            pen.circle(18.0, 5.0, 2.6, ic.paint[0], ink);
+            pen.circle(20.5, 11.0, 2.6, ic.paint[1], ink);
+            pen.circle(19.0, 17.5, 2.6, ic.paint[2], ink);
         }
         "warning" => {
-            pen.poly(&[(12.0, 3.0), (21.0, 20.0), (3.0, 20.0)], Color32::from_rgb(250, 200, 60), ink);
+            pen.poly(&[(12.0, 3.0), (21.0, 20.0), (3.0, 20.0)], ic.warning, ink);
             pen.line(&[(12.0, 9.0), (12.0, 14.0)], ink);
             pen.dot(12.0, 17.0, ink);
         }
diff --git a/assets/icons/ui/source/markers.rs b/assets/icons/ui/source/markers.rs
index 862b2996..1cf8ec84 100644
--- a/assets/icons/ui/source/markers.rs
+++ b/assets/icons/ui/source/markers.rs
@@ -5,8 +5,9 @@ use egui::{Color32, Pos2, Stroke, vec2};
 
 pub(crate) fn snap(painter: &egui::Painter, c: Pos2, tip: Option<Pos2>, kind: SnapKind, col: Color32, tag: Option<&str>) {
     // A dark halo under every stroke keeps the glyph readable on light and dark faces alike.
-    let halo = Stroke::new(4.5, Color32::from_black_alpha(150));
-    let white = Stroke::new(1.5, Color32::WHITE);
+    let ic = Tokens::get().icons;
+    let halo = Stroke::new(4.5, ic.marker_halo);
+    let white = Stroke::new(1.5, ic.highlight);
     if let Some(tip) = tip {
         let d = (tip - c).normalized();
         let n = vec2(-d.y, d.x);
@@ -30,7 +31,7 @@ pub(crate) fn snap(painter: &egui::Painter, c: Pos2, tip: Option<Pos2>, kind: Sn
             }
         }
     };
-    painter.add(shape(Color32::from_black_alpha(150), Stroke::NONE, 4.0));
+    painter.add(shape(ic.marker_halo, Stroke::NONE, 4.0));
     painter.add(shape(col, Stroke::NONE, 0.0));
     match kind {
         SnapKind::FaceCenter => {
@@ -38,8 +39,8 @@ pub(crate) fn snap(painter: &egui::Painter, c: Pos2, tip: Option<Pos2>, kind: Sn
         }
         SnapKind::CircleCenter => {
             painter.circle_stroke(c, 7.0, white);
-            painter.line_segment([c - vec2(4.5, 0.0), c + vec2(4.5, 0.0)], Stroke::new(1.2, Color32::WHITE));
-            painter.line_segment([c - vec2(0.0, 4.5), c + vec2(0.0, 4.5)], Stroke::new(1.2, Color32::WHITE));
+            painter.line_segment([c - vec2(4.5, 0.0), c + vec2(4.5, 0.0)], Stroke::new(1.2, ic.highlight));
+            painter.line_segment([c - vec2(0.0, 4.5), c + vec2(0.0, 4.5)], Stroke::new(1.2, ic.highlight));
         }
         SnapKind::EdgeMid | SnapKind::Vertex => {
             painter.add(shape(Color32::TRANSPARENT, white, 0.0));
diff --git a/assets/icons/ui/source/navigation.rs b/assets/icons/ui/source/navigation.rs
index fcef90a7..234b7e24 100644
--- a/assets/icons/ui/source/navigation.rs
+++ b/assets/icons/ui/source/navigation.rs
@@ -151,13 +151,12 @@ pub(crate) fn curved_arrow(painter: &egui::Painter, at: Pos2, clockwise: bool, h
 pub(crate) const AXIS_RADIUS: f32 = 11.0;
 pub(crate) fn axis_tip(painter: &egui::Painter, c: Pos2, name: &str, d: &Vec3, at: Pos2, depth: f64, hovered: bool, t: Tokens) {
     let col = if d.x != 0.0 {
-        solidcraft_engine::view::colors::AXIS_X
+        t.triad[0]
     } else if d.y != 0.0 {
-        solidcraft_engine::view::colors::AXIS_Y
+        t.triad[1]
     } else {
-        solidcraft_engine::view::colors::AXIS_Z
+        t.triad[2]
     };
-    let col = Color32::from_rgb(col.0, col.1, col.2);
     let positive = !name.starts_with('-');
     let ink = if depth < -0.01 { col.gamma_multiply(0.55) } else { col };
     painter.line_segment([c, at], Stroke::new(if positive { 2.0 } else { 1.0 }, ink));
diff --git a/assets/icons/ui/source/pointer.rs b/assets/icons/ui/source/pointer.rs
index 1dbb8baf..b637f753 100644
--- a/assets/icons/ui/source/pointer.rs
+++ b/assets/icons/ui/source/pointer.rs
@@ -1,14 +1,18 @@
 //! Original agent pointer and label. Animation stays with the UI controller.
 use egui::{Color32, FontId, Pos2, Shape, Stroke, vec2};
-pub(crate) const AGENT: Color32 = Color32::from_rgb(168, 85, 247);
+/// The agent pointer's colour (a theme token, so a colour vision mode can reach it).
+pub(crate) fn agent() -> Color32 {
+    crate::theme::Tokens::get().icons.agent
+}
 pub(crate) fn paint(painter: &egui::Painter, p: Pos2) {
+    let ic = crate::theme::Tokens::get().icons;
     // An arrow pointer, tip at `p`.
     let pts: Vec<Pos2> =
         [(0.0, 0.0), (0.0, 17.0), (4.5, 13.0), (7.5, 20.0), (10.5, 18.8), (7.5, 12.0), (13.0, 12.0)].iter().map(|(x, y)| p + vec2(*x, *y)).collect();
-    painter.add(Shape::convex_polygon(pts.clone(), AGENT, Stroke::NONE));
-    painter.add(Shape::closed_line(pts, Stroke::new(1.5, Color32::WHITE)));
-    let label = painter.layout_no_wrap("Agent".into(), FontId::proportional(11.0), Color32::WHITE);
+    painter.add(Shape::convex_polygon(pts.clone(), ic.agent, Stroke::NONE));
+    painter.add(Shape::closed_line(pts, Stroke::new(1.5, ic.highlight)));
+    let label = painter.layout_no_wrap("Agent".into(), FontId::proportional(11.0), ic.highlight);
     let r = egui::Rect::from_min_size(p + vec2(15.0, 18.0), label.size() + vec2(10.0, 4.0));
-    painter.rect_filled(r, 4.0, AGENT);
-    painter.galley(r.min + vec2(5.0, 2.0), label, Color32::WHITE);
+    painter.rect_filled(r, 4.0, ic.agent);
+    painter.galley(r.min + vec2(5.0, 2.0), label, ic.highlight);
 }
diff --git a/assets/locales/de.json b/assets/locales/de.json
index a683ae0d..bda21b00 100644
--- a/assets/locales/de.json
+++ b/assets/locales/de.json
@@ -72,6 +72,21 @@
   "ui.coincident": "Koinzident",
   "ui.collapse": "Einklappen",
   "ui.collinear": "Kollinear",
+  "ui.colour_vision": "Farbsehen",
+  "ui.colour_vision_deutan": "Deutan",
+  "ui.colour_vision_deutan_tip": "Bei schwachem oder fehlendem Grünsinn",
+  "ui.colour_vision_failed": "Fehler",
+  "ui.colour_vision_fixed": "Fixiert",
+  "ui.colour_vision_mode": "Modus",
+  "ui.colour_vision_note": "Ändert die Farben, die eine Bedeutung tragen: Skizzenstatus, Achsen, Biegungen, Analysen und Symbole. Wenn Sie die Farbfilter von Windows verwenden, lassen Sie dies auf „Aus“.",
+  "ui.colour_vision_off": "Aus",
+  "ui.colour_vision_off_tip": "Die eigenen Farben des Designs",
+  "ui.colour_vision_projected": "Projiziert",
+  "ui.colour_vision_protan": "Protan",
+  "ui.colour_vision_protan_tip": "Bei schwachem oder fehlendem Rotsinn",
+  "ui.colour_vision_sample": "Beispiel",
+  "ui.colour_vision_tritan": "Tritan",
+  "ui.colour_vision_tritan_tip": "Bei schwachem oder fehlendem Blausinn",
   "ui.combine": "Kombinieren",
   "ui.coming_later": "bald verfügbar",
   "ui.concentric": "Konzentrisch",
@@ -668,6 +683,7 @@
   "ui.heading_constraints": "RANDBEDINGUNGEN",
   "ui.heading_utilities": "WERKZEUGE",
   "BROWSER": "BROWSER",
+  "Bends": "Biegungen",
   "Drive Joint": "Gelenk antreiben",
   "Edit Profile Sketch": "Profile-Skizze bearbeiten",
   "Find in Browser": "Im Browser suchen",
diff --git a/assets/locales/en.json b/assets/locales/en.json
index 2f2e6471..81df1f95 100644
--- a/assets/locales/en.json
+++ b/assets/locales/en.json
@@ -350,6 +350,21 @@
   "ui.coincident": "Coincident",
   "ui.collapse": "Collapse",
   "ui.collinear": "Collinear",
+  "ui.colour_vision": "Colour vision",
+  "ui.colour_vision_deutan": "Deutan",
+  "ui.colour_vision_deutan_tip": "For a weak or missing green sense",
+  "ui.colour_vision_failed": "Failed",
+  "ui.colour_vision_fixed": "Fixed",
+  "ui.colour_vision_mode": "Mode",
+  "ui.colour_vision_note": "Changes the colours that carry a meaning: sketch states, axes, bends, analyses and icons. If you use Windows colour filters, keep this Off.",
+  "ui.colour_vision_off": "Off",
+  "ui.colour_vision_off_tip": "The theme's own colours",
+  "ui.colour_vision_projected": "Projected",
+  "ui.colour_vision_protan": "Protan",
+  "ui.colour_vision_protan_tip": "For a weak or missing red sense",
+  "ui.colour_vision_sample": "Sample",
+  "ui.colour_vision_tritan": "Tritan",
+  "ui.colour_vision_tritan_tip": "For a weak or missing blue sense",
   "ui.combine": "Combine",
   "ui.coming_later": "coming later",
   "ui.concentric": "Concentric",
diff --git a/assets/locales/ja.json b/assets/locales/ja.json
index 4d19b5c4..2f5f8973 100644
--- a/assets/locales/ja.json
+++ b/assets/locales/ja.json
@@ -350,6 +350,21 @@
   "ui.coincident": "一致",
   "ui.collapse": "折りたたむ",
   "ui.collinear": "同一直線上",
+  "ui.colour_vision": "色覚",
+  "ui.colour_vision_deutan": "2型色覚（D型）",
+  "ui.colour_vision_deutan_tip": "緑を感じにくい、または感じない場合に",
+  "ui.colour_vision_failed": "エラー",
+  "ui.colour_vision_fixed": "固定",
+  "ui.colour_vision_mode": "モード",
+  "ui.colour_vision_note": "意味を持つ色を変更します（スケッチの状態、軸、曲げ、解析、アイコン）。Windows のカラー フィルターを使う場合は「オフ」のままにしてください。",
+  "ui.colour_vision_off": "オフ",
+  "ui.colour_vision_off_tip": "テーマ本来の色",
+  "ui.colour_vision_projected": "投影",
+  "ui.colour_vision_protan": "1型色覚（P型）",
+  "ui.colour_vision_protan_tip": "赤を感じにくい、または感じない場合に",
+  "ui.colour_vision_sample": "サンプル",
+  "ui.colour_vision_tritan": "3型色覚（T型）",
+  "ui.colour_vision_tritan_tip": "青を感じにくい、または感じない場合に",
   "ui.combine": "結合",
   "ui.coming_later": "準備中",
   "ui.concentric": "同心",
diff --git a/assets/locales/ko.json b/assets/locales/ko.json
index f8d148ef..9ef6ccaf 100644
--- a/assets/locales/ko.json
+++ b/assets/locales/ko.json
@@ -72,6 +72,21 @@
   "ui.coincident": "일치",
   "ui.collapse": "접기",
   "ui.collinear": "동일 선상",
+  "ui.colour_vision": "색각",
+  "ui.colour_vision_deutan": "녹색각이상 (Deutan)",
+  "ui.colour_vision_deutan_tip": "녹색 감각이 약하거나 없는 경우",
+  "ui.colour_vision_failed": "실패",
+  "ui.colour_vision_fixed": "고정",
+  "ui.colour_vision_mode": "모드",
+  "ui.colour_vision_note": "의미를 나타내는 색을 바꿉니다: 스케치 상태, 축, 벤딩, 분석, 아이콘. Windows 색 필터를 사용한다면 '끄기'로 두세요.",
+  "ui.colour_vision_off": "끄기",
+  "ui.colour_vision_off_tip": "테마 고유의 색상",
+  "ui.colour_vision_projected": "투영",
+  "ui.colour_vision_protan": "적색각이상 (Protan)",
+  "ui.colour_vision_protan_tip": "빨간색 감각이 약하거나 없는 경우",
+  "ui.colour_vision_sample": "예시",
+  "ui.colour_vision_tritan": "청색각이상 (Tritan)",
+  "ui.colour_vision_tritan_tip": "파란색 감각이 약하거나 없는 경우",
   "ui.combine": "결합",
   "ui.coming_later": "추후 지원 예정",
   "ui.concentric": "동심",
@@ -668,6 +683,7 @@
   "ui.heading_constraints": "구속 조건",
   "ui.heading_utilities": "유틸리티",
   "BROWSER": "브라우저",
+  "Bends": "벤딩",
   "Drive Joint": "조인트 구동",
   "Edit Profile Sketch": "윤곽 스케치 편집",
   "Find in Browser": "브라우저에서 찾기",
diff --git a/assets/locales/ru.json b/assets/locales/ru.json
index d5c55210..087d06ee 100644
--- a/assets/locales/ru.json
+++ b/assets/locales/ru.json
@@ -342,6 +342,21 @@
   "ui.coincident": "Совпадение",
   "ui.collapse": "Свернуть",
   "ui.collinear": "Коллинеарность",
+  "ui.colour_vision": "Цветовое зрение",
+  "ui.colour_vision_deutan": "Дейтан",
+  "ui.colour_vision_deutan_tip": "При слабом или отсутствующем восприятии зелёного",
+  "ui.colour_vision_failed": "Ошибка",
+  "ui.colour_vision_fixed": "Фиксировано",
+  "ui.colour_vision_mode": "Режим",
+  "ui.colour_vision_note": "Меняет цвета, которые несут смысл: статус эскиза, оси, гибы, анализы и значки. Если вы пользуетесь цветовыми фильтрами Windows, оставьте «Выключено».",
+  "ui.colour_vision_off": "Выключено",
+  "ui.colour_vision_off_tip": "Собственные цвета темы",
+  "ui.colour_vision_projected": "Проекция",
+  "ui.colour_vision_protan": "Протан",
+  "ui.colour_vision_protan_tip": "При слабом или отсутствующем восприятии красного",
+  "ui.colour_vision_sample": "Пример",
+  "ui.colour_vision_tritan": "Тритан",
+  "ui.colour_vision_tritan_tip": "При слабом или отсутствующем восприятии синего",
   "ui.combine": "Объединение",
   "ui.coming_later": "появится позже",
   "ui.concentric": "Концентричность",
diff --git a/assets/locales/zh.json b/assets/locales/zh.json
index 5cb7ddb6..4a8d7e74 100644
--- a/assets/locales/zh.json
+++ b/assets/locales/zh.json
@@ -349,6 +349,21 @@
   "ui.coincident": "重合",
   "ui.collapse": "折叠",
   "ui.collinear": "共线",
+  "ui.colour_vision": "色觉",
+  "ui.colour_vision_deutan": "绿色觉异常（Deutan）",
+  "ui.colour_vision_deutan_tip": "绿色感知较弱或缺失时使用",
+  "ui.colour_vision_failed": "失败",
+  "ui.colour_vision_fixed": "固定",
+  "ui.colour_vision_mode": "模式",
+  "ui.colour_vision_note": "更改表示含义的颜色：草图状态、轴、折弯、分析和图标。如果使用 Windows 颜色滤镜，请保持“关闭”。",
+  "ui.colour_vision_off": "关闭",
+  "ui.colour_vision_off_tip": "主题本身的颜色",
+  "ui.colour_vision_projected": "投影",
+  "ui.colour_vision_protan": "红色觉异常（Protan）",
+  "ui.colour_vision_protan_tip": "红色感知较弱或缺失时使用",
+  "ui.colour_vision_sample": "示例",
+  "ui.colour_vision_tritan": "蓝色觉异常（Tritan）",
+  "ui.colour_vision_tritan_tip": "蓝色感知较弱或缺失时使用",
   "ui.combine": "组合",
   "ui.coming_later": "即将推出",
   "ui.concentric": "同心",
diff --git a/assets/shaders/viewport.wgsl b/assets/shaders/viewport.wgsl
index e1d7d591..97c3c479 100644
--- a/assets/shaders/viewport.wgsl
+++ b/assets/shaders/viewport.wgsl
@@ -10,6 +10,10 @@ struct U {
     acc_u: vec4<f32>,  // accessibility map axes (xyz, offset)
     acc_v: vec4<f32>,
     eye: vec4<f32>,    // eye position, w = 1 for perspective (0: orthographic, looking along -back)
+    // analysis colours (`theme::AnalysisColors`): draft positive, between, negative; reachable,
+    // blocked; curvature flat, middle, tight
+    ana_c: array<vec4<f32>, 8>,
+    ana_f: vec4<f32>,  // x = 1: stripe the negative draft and blocked faces
 };
 
 @group(1) @binding(2) var acc_t: texture_2d<f32>;
@@ -150,8 +154,8 @@ fn analysis(i: TOut, k: f32) -> vec4<f32> {
         // Slack of a pixel and a half, more on slopes (the map holds the pixel's highest point).
         let slack = u.ana.y * (1.0 + sqrt(max(1.0 - cn * cn, 0.0)) / max(cn, 0.05));
         let clear = dot(i.wp, d) >= top - slack;
-        var c = vec3<f32>(0.85, 0.22, 0.20);
-        if (facing && clear) { c = vec3<f32>(0.20, 0.75, 0.30); }
+        var c = u.ana_c[4].rgb;
+        if (facing && clear) { c = u.ana_c[3].rgb; } else { c = stripe(i, c); }
         return out_color(vec4<f32>(c * lit, 1.0));
     }
     if (u.ana.x > 3.5) {
@@ -171,18 +175,25 @@ fn analysis(i: TOut, k: f32) -> vec4<f32> {
     }
     if (u.ana.x < 2.5) {
         let a = degrees(asin(clamp(dot(normalize(i.n), normalize(u.pull.xyz)), -1.0, 1.0)));
-        var c = vec3<f32>(0.95, 0.80, 0.15);
-        if (a >= u.ana.y) { c = vec3<f32>(0.20, 0.75, 0.30); }
-        if (a <= -u.ana.y) { c = vec3<f32>(0.85, 0.22, 0.20); }
+        var c = u.ana_c[1].rgb;
+        if (a >= u.ana.y) { c = u.ana_c[0].rgb; }
+        if (a <= -u.ana.y) { c = stripe(i, u.ana_c[2].rgb); }
         return out_color(vec4<f32>(c * lit, 1.0));
     }
     // Curvature from how fast the normal turns across the pixel.
     let t = clamp(k * u.ana.y, 0.0, 1.0);
-    let c = select(mix(vec3<f32>(0.10, 0.80, 0.25), vec3<f32>(0.90, 0.15, 0.10), t * 2.0 - 1.0),
-                   mix(vec3<f32>(0.15, 0.35, 0.95), vec3<f32>(0.10, 0.80, 0.25), t * 2.0), t < 0.5);
+    let c = select(mix(u.ana_c[6].rgb, u.ana_c[7].rgb, t * 2.0 - 1.0), mix(u.ana_c[5].rgb, u.ana_c[6].rgb, t * 2.0), t < 0.5);
     return out_color(vec4<f32>(c * lit, 1.0));
 }
 
+/// A "bad" analysis face (negative draft, blocked): with the stripes on (colour vision modes), the
+/// section cap's 45 degree hatch over it, so colour is not the only cue.
+fn stripe(i: TOut, c: vec3<f32>) -> vec3<f32> {
+    if (u.ana_f.x < 0.5) { return c; }
+    let h = fract((i.pos.x + i.pos.y) / 9.0);
+    return select(c, c * 0.6, h < 0.22);
+}
+
 @fragment
 fn fs_tri(i: TOut) -> @location(0) vec4<f32> {
     if (clipped(i.wp)) { discard; }
diff --git a/assets/styles/ui/palettes.rs b/assets/styles/ui/palettes.rs
index 580c75aa..310a07da 100644
--- a/assets/styles/ui/palettes.rs
+++ b/assets/styles/ui/palettes.rs
@@ -1,5 +1,5 @@
 //! Original light and dark palette values. Compiled by the UI theme boundary.
-use crate::theme::Tokens;
+use crate::theme::{AnalysisColors, IconColors, Tokens};
 use egui::Color32;
 impl Tokens {
     pub const fn light() -> Tokens {
@@ -83,6 +83,48 @@ impl Tokens {
             field: Color32::WHITE,
             box_window: Color32::from_rgb(38, 120, 218),
             box_crossing: Color32::from_rgb(40, 160, 80),
+            // Equal to `view::colors` (the engine's tags), so mapping a tag to its token
+            // changes nothing.
+            sketch_projected: Color32::from_rgb(150, 60, 190),
+            sketch_lost: Color32::from_rgb(200, 60, 90),
+            sketch_construction: Color32::from_rgb(230, 130, 40),
+            sketch_centerline: Color32::from_rgb(200, 110, 60),
+            triad: [Color32::from_rgb(220, 60, 60), Color32::from_rgb(60, 170, 60), Color32::from_rgb(60, 100, 230)],
+            gizmo: [Color32::from_rgb(225, 70, 60), Color32::from_rgb(80, 190, 80), Color32::from_rgb(70, 130, 240)],
+            bend_up: Color32::from_rgb(30, 140, 50),
+            bend_down: Color32::from_rgb(200, 90, 20),
+            interference: Color32::from_rgb(235, 45, 40),
+            analysis: AnalysisColors {
+                draft: [[0.20, 0.75, 0.30], [0.95, 0.80, 0.15], [0.85, 0.22, 0.20]],
+                access: [[0.20, 0.75, 0.30], [0.85, 0.22, 0.20]],
+                curvature: [[0.15, 0.35, 0.95], [0.10, 0.80, 0.25], [0.90, 0.15, 0.10]],
+                hatch: false,
+            },
+            icons: IconColors {
+                sheet: Color32::from_rgb(170, 200, 240),
+                sheet_2: Color32::from_rgb(150, 185, 235),
+                sheet_light: Color32::from_rgb(214, 229, 248),
+                sheet_line: Color32::from_rgb(127, 166, 218),
+                highlight: Color32::WHITE,
+                glint: Color32::from_rgba_premultiplied(160, 160, 160, 160),
+                folder: Color32::from_rgb(236, 200, 110),
+                plane: Color32::from_rgb(244, 214, 150),
+                fold: Color32::from_rgb(130, 140, 160),
+                stripe: Color32::from_gray(30),
+                sky: Color32::from_rgb(190, 205, 230),
+                floor: Color32::from_rgb(60, 62, 70),
+                paint: [Color32::from_rgb(220, 70, 60), Color32::from_rgb(70, 150, 230), Color32::from_rgb(240, 200, 60)],
+                axes: [Color32::from_rgb(210, 60, 60), Color32::from_rgb(60, 160, 60), Color32::from_rgb(60, 100, 220)],
+                access: [Color32::from_rgb(70, 180, 90), Color32::from_rgb(220, 70, 60)],
+                draft: [Color32::from_rgb(70, 180, 90), Color32::from_rgb(235, 200, 50)],
+                curvature: [Color32::from_rgb(60, 110, 230), Color32::from_rgb(70, 190, 90), Color32::from_rgb(225, 60, 45)],
+                interference: Color32::from_rgb(225, 70, 60),
+                warning: Color32::from_rgb(250, 200, 60),
+                agent: Color32::from_rgb(168, 85, 247),
+                marker_halo: Color32::from_black_alpha(150),
+            },
+            app_bar_icon: [Color32::from_rgb(225, 230, 238), Color32::from_rgb(120, 140, 170), Color32::from_rgb(120, 190, 255)],
+            logo: [Color32::from_rgb(96, 158, 236), Color32::from_rgb(58, 136, 238), Color32::from_rgb(55, 108, 197), Color32::WHITE],
         }
     }
     pub const fn dark() -> Tokens {
@@ -135,6 +177,60 @@ impl Tokens {
         t.field = Color32::from_rgb(30, 34, 41);
         t.box_window = Color32::from_rgb(70, 150, 255);
         t.box_crossing = Color32::from_rgb(80, 200, 120);
+        t.bend_up = Color32::from_rgb(110, 200, 120);
+        t.bend_down = Color32::from_rgb(240, 150, 80);
+        t
+    }
+
+    /// Colour vision, red-green (Protan and Deutan share it, #778): values of the theme's colours
+    /// that a weak red or green sense still tells apart. Each was measured against normal vision,
+    /// protan and deutan, with two simulations of each loss (`colour_vision_tests`).
+    pub(super) const fn red_green(self, dark: bool) -> Tokens {
+        let mut t = self;
+        let positive = [0.20, 0.45, 0.90];
+        let negative = [0.85, 0.40, 0.05];
+        t.triad[0] = Color32::from_rgb(200, 40, 40);
+        t.triad[1] = Color32::from_rgb(120, 210, 80);
+        t.gizmo[1] = Color32::from_rgb(140, 220, 90);
+        t.preview_sketch = Color32::from_rgb(80, 185, 145);
+        t.analysis.draft = [positive, [0.95, 0.90, 0.60], negative];
+        t.analysis.access = [positive, negative];
+        t.analysis.hatch = true;
+        // The icons that show the same meanings follow; on the dark toolbar the blue is a little
+        // stronger, to stay clear of the icon fill.
+        let good = if dark { Color32::from_rgb(35, 115, 245) } else { Color32::from_rgb(51, 115, 230) };
+        t.icons.axes[0] = t.triad[0];
+        t.icons.axes[1] = t.triad[1];
+        t.icons.access = [good, Color32::from_rgb(217, 102, 13)];
+        t.icons.draft = [good, Color32::from_rgb(242, 230, 153)];
+        if dark {
+            t.bend_up = Color32::from_rgb(110, 165, 255);
+            t.bend_down = Color32::from_rgb(240, 180, 70);
+            t.sketch_accent = Color32::from_rgb(150, 225, 195);
+        } else {
+            t.sketch_projected = Color32::from_rgb(205, 120, 215);
+            t.sketch_locked = Color32::from_rgb(60, 150, 120);
+            t.timeline_item_error = Color32::from_rgb(232, 196, 170);
+            t.bend_up = Color32::from_rgb(30, 100, 210);
+            t.bend_down = Color32::from_rgb(200, 120, 0);
+            t.sketch_accent = Color32::from_rgb(60, 150, 105);
+        }
+        t
+    }
+
+    /// Colour vision, blue-yellow (Tritan, #778), measured against normal vision and tritan.
+    pub(super) const fn blue_yellow(self, dark: bool) -> Tokens {
+        let mut t = self;
+        t.analysis.hatch = true;
+        t.preview_sketch = Color32::from_rgb(125, 180, 105);
+        if dark {
+            t.sketch_locked = Color32::from_rgb(140, 225, 110);
+            t.box_crossing = Color32::from_rgb(240, 110, 170);
+            t.glyph_text = Color32::from_rgb(240, 180, 165);
+        } else {
+            t.sketch_locked = Color32::from_rgb(20, 165, 70);
+            t.box_crossing = Color32::from_rgb(200, 60, 120);
+        }
         t
     }
 }
diff --git a/crates/ui-egui/src/agent_cursor.rs b/crates/ui-egui/src/agent_cursor.rs
index daf27398..676ab5e0 100644
--- a/crates/ui-egui/src/agent_cursor.rs
+++ b/crates/ui-egui/src/agent_cursor.rs
@@ -334,7 +334,7 @@ fn finish(app: &mut SolveApp, ctx: &egui::Context) {
 }
 
 /// The pointer's colour: a violet no part of the UI uses.
-use crate::icons::pointer::AGENT;
+use crate::icons::pointer::agent;
 
 /// Draw the pointer, its "Agent" tag and the click ripples over everything.
 pub fn paint(app: &SolveApp, ctx: &egui::Context) {
@@ -345,7 +345,7 @@ pub fn paint(app: &SolveApp, ctx: &egui::Context) {
     let painter = ctx.layer_painter(egui::LayerId::new(egui::Order::Debug, egui::Id::new("sc_agent_cursor")));
     for (at, t0) in &app.agent.ripples {
         let k = ((app.now - t0) / 0.6).clamp(0.0, 1.0) as f32;
-        painter.circle_stroke(*at, 6.0 + 22.0 * k, Stroke::new(3.0 * (1.0 - k) + 0.5, AGENT.gamma_multiply(1.0 - k)));
+        painter.circle_stroke(*at, 6.0 + 22.0 * k, Stroke::new(3.0 * (1.0 - k) + 0.5, agent().gamma_multiply(1.0 - k)));
     }
     crate::icons::pointer::paint(&painter, p);
 }
diff --git a/crates/ui-egui/src/colour_tokens_tests.rs b/crates/ui-egui/src/colour_tokens_tests.rs
new file mode 100644
index 00000000..a2d892e4
--- /dev/null
+++ b/crates/ui-egui/src/colour_tokens_tests.rs
@@ -0,0 +1,303 @@
+//! Every colour that carries a meaning comes from `theme::Tokens` (#778): the engine's sketch and
+//! axis tags, the surface analysis colours and every colour an icon draws. These tests hold that
+//! the tokens equal what was drawn before, and that a new colour cannot skip them.
+
+use egui::{Color32, Pos2, Rect, vec2};
+use solidcraft_engine::render::Rgb;
+use solidcraft_engine::view::colors;
+
+use crate::theme::{IconColors, Tokens};
+
+fn rgb(c: Rgb) -> Color32 {
+    Color32::from_rgb(c.0, c.1, c.2)
+}
+
+/// The new tokens hold exactly the values that were drawn in place before they were tokens, so
+/// with no colour vision mode on, nothing on screen changes.
+#[test]
+fn moved_colours_keep_the_values_they_were_drawn_with() {
+    for t in [Tokens::light(), Tokens::dark()] {
+        assert_eq!(t.sketch_projected, rgb(colors::SKETCH_PROJECTED));
+        assert_eq!(t.sketch_lost, rgb(colors::SKETCH_LOST));
+        assert_eq!(t.sketch_construction, rgb(colors::SKETCH_CONSTRUCTION));
+        assert_eq!(t.sketch_centerline, rgb(colors::SKETCH_CENTERLINE));
+        assert_eq!(t.triad, [rgb(colors::AXIS_X), rgb(colors::AXIS_Y), rgb(colors::AXIS_Z)]);
+        assert_eq!(t.gizmo, [Color32::from_rgb(225, 70, 60), Color32::from_rgb(80, 190, 80), Color32::from_rgb(70, 130, 240)]);
+        assert_eq!(t.interference, Color32::from_rgb(235, 45, 40));
+        // The shader's former literals, bit for bit.
+        assert_eq!(t.analysis.draft, [[0.20, 0.75, 0.30], [0.95, 0.80, 0.15], [0.85, 0.22, 0.20]]);
+        assert_eq!(t.analysis.access, [[0.20, 0.75, 0.30], [0.85, 0.22, 0.20]]);
+        assert_eq!(t.analysis.curvature, [[0.15, 0.35, 0.95], [0.10, 0.80, 0.25], [0.90, 0.15, 0.10]]);
+        assert!(!t.analysis.hatch);
+        assert_eq!(t.app_bar_icon, [Color32::from_rgb(225, 230, 238), Color32::from_rgb(120, 140, 170), Color32::from_rgb(120, 190, 255)]);
+        assert_eq!(t.logo, [Color32::from_rgb(96, 158, 236), Color32::from_rgb(58, 136, 238), Color32::from_rgb(55, 108, 197), Color32::WHITE]);
+        assert_eq!(t.icons.glint, Color32::from_white_alpha(160));
+        assert_eq!(t.icons.marker_halo, Color32::from_black_alpha(150));
+        assert_eq!(t.icons.agent, Color32::from_rgb(168, 85, 247));
+    }
+    let (l, d) = (Tokens::light(), Tokens::dark());
+    assert_eq!((l.bend_up, l.bend_down), (Color32::from_rgb(30, 140, 50), Color32::from_rgb(200, 90, 20)));
+    assert_eq!((d.bend_up, d.bend_down), (Color32::from_rgb(110, 200, 120), Color32::from_rgb(240, 150, 80)));
+}
+
+/// The analysis colours reach the shader in the order its `ana_c` array reads them.
+#[test]
+fn analysis_colours_reach_the_shader_in_its_order() {
+    let a = Tokens::light().analysis;
+    let v = crate::gpu::analysis_colors(&a);
+    let at = |i: usize| [v[4 * i], v[4 * i + 1], v[4 * i + 2]];
+    assert_eq!([at(0), at(1), at(2)], a.draft);
+    assert_eq!([at(3), at(4)], a.access);
+    assert_eq!([at(5), at(6), at(7)], a.curvature);
+    assert!((0..8).all(|i| v[4 * i + 3] == 1.0));
+    assert_eq!(v[32], 0.0, "no stripes without a colour vision mode");
+    let mut striped = a;
+    striped.hatch = true;
+    assert_eq!(crate::gpu::analysis_colors(&striped)[32], 1.0);
+}
+
+/// Every name a `match` arm in the icon source draws.
+fn icon_names() -> Vec<&'static str> {
+    let src = include_str!("../../../assets/icons/ui/source/icons.rs");
+    let body = src.split("#[cfg(test)]").next().unwrap_or(src);
+    let mut names = Vec::new();
+    for line in body.lines() {
+        let line = line.trim_start();
+        if !line.starts_with('"') {
+            continue;
+        }
+        let Some((pattern, _)) = line.split_once("=>") else { continue };
+        let pattern = pattern.split(" if ").next().unwrap_or(pattern);
+        for part in pattern.split('|') {
+            let part = part.trim();
+            if part.len() > 2 && part.starts_with('"') && part.ends_with('"') {
+                names.push(&part[1..part.len() - 1]);
+            }
+        }
+    }
+    names.sort_unstable();
+    names.dedup();
+    names
+}
+
+/// Marker icon colours: every field its own colour, from `seed`.
+fn marker_icons(seed: u8) -> IconColors {
+    let c = |i: u8| Color32::from_rgb(seed, i, seed ^ i);
+    IconColors {
+        sheet: c(1),
+        sheet_2: c(2),
+        sheet_light: c(3),
+        sheet_line: c(4),
+        highlight: c(5),
+        glint: c(6),
+        folder: c(7),
+        plane: c(8),
+        fold: c(9),
+        stripe: c(10),
+        sky: c(11),
+        floor: c(12),
+        paint: [c(13), c(14), c(15)],
+        axes: [c(16), c(17), c(18)],
+        access: [c(19), c(20)],
+        draft: [c(21), c(22)],
+        curvature: [c(23), c(24), c(25)],
+        interference: c(26),
+        warning: c(27),
+        agent: c(28),
+        marker_halo: c(29),
+    }
+}
+
+/// The colours an icon draws (premultiplied `#RR_GG_BB_AA`, in drawing order).
+fn drawn_colours(name: &str, seed: u8) -> Vec<String> {
+    let ctx = egui::Context::default();
+    let input = egui::RawInput { screen_rect: Some(Rect::from_min_size(Pos2::ZERO, vec2(100.0, 100.0))), ..Default::default() };
+    let icons = marker_icons(seed);
+    let out = ctx.run_ui(input, |ui| {
+        let r = Rect::from_min_size(Pos2::ZERO, vec2(24.0, 24.0));
+        let ink = Color32::from_rgb(seed, 101, 1);
+        let fill = Color32::from_rgb(seed, 102, 2);
+        let accent = Color32::from_rgb(seed, 103, 3);
+        crate::icons::paint_with(ui.painter(), r, name, ink, fill, accent, &icons);
+    });
+    let text = format!("{:?}", out.shapes);
+    let b = text.as_bytes();
+    let mut colours = Vec::new();
+    for i in 0..b.len() {
+        let hex = |k: usize| b.get(i + k).is_some_and(u8::is_ascii_hexdigit);
+        if b[i] == b'#' && (1..=11).all(|k| if k % 3 == 0 { b.get(i + k) == Some(&b'_') } else { hex(k) }) {
+            colours.push(text[i..i + 12].to_string());
+        }
+    }
+    colours
+}
+
+/// "All icons past, present and future" follow the colour vision mode: an icon may draw only the
+/// colours its caller passes (ink, fill, accent) and the `IconColors` tokens, or colours made
+/// from them. Each icon is drawn twice with different marker colours; a colour that comes out the
+/// same both times was written into the icon, and a mode could not reach it.
+#[test]
+fn every_icon_draws_only_colours_a_mode_can_reach() {
+    let names = icon_names();
+    assert!(names.len() > 150, "icon names were not found in the icon source: {}", names.len());
+    let mut fixed = Vec::new();
+    for name in &names {
+        let (a, b) = (drawn_colours(name, 40), drawn_colours(name, 200));
+        assert_eq!(a.len(), b.len(), "{name}: the two drawings differ in shape");
+        for (x, y) in a.iter().zip(&b) {
+            if x == y && !x.ends_with("_00") {
+                fixed.push(format!("{name}: {x}"));
+            }
+        }
+    }
+    fixed.dedup();
+    assert!(fixed.is_empty(), "icons that draw a colour of their own: {fixed:?}");
+}
+
+/// The most colour literals each UI file may hold, and why. None of them carries a meaning that a
+/// colour vision mode must change. A file with more fails here: make the new colour a token in
+/// `theme::Tokens` (and `assets/styles/ui/palettes.rs`) instead, or, if it carries no meaning,
+/// raise the file's count here and give the reason. Fewer is always fine. The icon sources may
+/// hold none at all.
+const ALLOWED_LITERALS: &[(&str, usize, &str)] = &[
+    ("navigation.rs", 1, "the navigation cube's face shading, made from a token"),
+    ("canvas.rs", 3, "white rings around manipulator handles"),
+    ("context_menu.rs", 1, "the radial menu's shadow"),
+    ("dialogs_appearance.rs", 1, "a design appearance: the colour is the fact"),
+    ("dialogs_library.rs", 1, "a library appearance's swatch: the colour is the fact"),
+    ("dialogs_assembly.rs", 1, "the interference fill, shaded from its token"),
+    ("dialogs_motion.rs", 1, "a white outline"),
+    ("documents.rs", 4, "white hover overlays on document tabs"),
+    ("frame.rs", 1, "the window shadow"),
+    ("gizmo.rs", 2, "the gizmo's neutral grey ball"),
+    ("home.rs", 4, "white ink on accent buttons, and thumbnail tints"),
+    ("ref_images.rs", 1, "a reference image's opacity tint"),
+    ("sketch_palette.rs", 1, "white text on the accent button"),
+    ("sketch_text.rs", 1, "white text on the selection chip"),
+    ("titlebar.rs", 4, "the window close button's red hover (the system's convention), white hovers and ink"),
+    ("toolbar.rs", 3, "white hover overlays and the version text"),
+    ("update.rs", 1, "text laid out only to measure its width, never drawn"),
+];
+
+const COLOUR_LITERALS: &[&str] = &[
+    "Color32::from_rgb(",
+    "Color32::from_rgba_unmultiplied(",
+    "Color32::from_rgba_unmultiplied_const(",
+    "Color32::from_rgba_premultiplied(",
+    "Color32::from_gray(",
+    "Color32::from_black_alpha(",
+    "Color32::from_white_alpha(",
+    "Color32::from_hex(",
+    "Color32::WHITE",
+    "Color32::BLACK",
+    "Color32::RED",
+    "Color32::GREEN",
+    "Color32::BLUE",
+    "Color32::YELLOW",
+    "Color32::GOLD",
+    "Color32::ORANGE",
+    "Color32::BROWN",
+    "Color32::KHAKI",
+    "Color32::GRAY",
+    "Color32::LIGHT_GRAY",
+    "Color32::DARK_GRAY",
+    "Color32::DARK_RED",
+    "Color32::LIGHT_RED",
+    "Color32::DARK_BLUE",
+    "Color32::LIGHT_BLUE",
+    "Color32::DARK_GREEN",
+    "Color32::LIGHT_GREEN",
+    "Color32::LIGHT_YELLOW",
+];
+
+#[test]
+fn colours_outside_the_theme_are_only_the_listed_neutral_ones() {
+    let root = std::path::Path::new(env!("CARGO_MANIFEST_DIR"));
+    let dirs = [root.join("src"), root.join("../../assets/icons/ui/source")];
+    let mut found = Vec::new();
+    for dir in &dirs {
+        let entries = std::fs::read_dir(dir).unwrap_or_else(|e| panic!("{}: {e}", dir.display()));
+        for entry in entries.flatten() {
+            let path = entry.path();
+            let name = path.file_name().and_then(|n| n.to_str()).unwrap_or_default().to_string();
+            if !name.ends_with(".rs") || name.ends_with("_tests.rs") || name == "theme.rs" {
+                continue;
+            }
+            let src = std::fs::read_to_string(&path).unwrap_or_default();
+            let code = src.split("#[cfg(test)]").next().unwrap_or(&src);
+            let n: usize = COLOUR_LITERALS.iter().map(|p| code.matches(p).count()).sum();
+            let allowed = ALLOWED_LITERALS.iter().find(|(f, _, _)| *f == name).map_or(0, |(_, n, _)| *n);
+            if n > allowed {
+                found.push(format!("{name}: {n} colour literal(s), at most {allowed} allowed"));
+            }
+        }
+    }
+    assert!(found.is_empty(), "colour literals outside theme::Tokens: {found:?}");
+}
+
+/// The analysis shader takes its colours from the uniform (and so from the tokens). Only the
+/// zebra and environment map neutrals and direction vectors stay as literals.
+#[test]
+fn analysis_shader_colours_come_from_the_uniform() {
+    let src = include_str!("../../../assets/shaders/viewport.wgsl");
+    let start = src.find("fn analysis(").unwrap_or(0);
+    let end = src.find("fn stripe(").unwrap_or(src.len());
+    let body = &src[start..end];
+    let mut literals = Vec::new();
+    let mut rest = body;
+    while let Some(i) = rest.find("vec3<f32>(") {
+        let tail = &rest[i..];
+        let close = tail.find(')').unwrap_or(tail.len() - 1);
+        literals.push(&tail[..=close]);
+        rest = &tail[close..];
+    }
+    assert_eq!(
+        literals,
+        [
+            "vec3<f32>(0.0, 0.0, 1.0)",
+            "vec3<f32>(1.0, 0.0, 0.0)",
+            "vec3<f32>(c)",
+            "vec3<f32>(0.32, 0.34, 0.38)",
+            "vec3<f32>(0.80, 0.86, 0.95)",
+            "vec3<f32>(0.6)",
+            "vec3<f32>(0.9)",
+            "vec3<f32>(0.55, 0.56, 0.60)",
+            "vec3<f32>(0.20, 0.20, 0.22)",
+            "vec3<f32>(0.35)",
+            "vec3<f32>(1.0)",
+        ],
+        "a new colour in the analysis shader must come from `ana_c` (theme::AnalysisColors)"
+    );
+    assert_eq!(body.matches("u.ana_c[").count(), 9, "every analysis colour reads `ana_c`");
+}
+
+/// Every colour the engine tags a scene line with is mapped to a token by the viewport, or carries
+/// no meaning a colour vision mode must change. A new engine tag fails here until it is placed.
+#[test]
+fn every_engine_colour_tag_is_placed() {
+    const MAPPED: &[&str] = &[
+        "SKETCH",
+        "SKETCH_DONE",
+        "SKETCH_FIXED",
+        "SKETCH_LOCKED",
+        "SKETCH_PROJECTED",
+        "SKETCH_LOST",
+        "SKETCH_CONSTRUCTION",
+        "SKETCH_CENTERLINE",
+        "AXIS_X",
+        "AXIS_Y",
+        "AXIS_Z",
+    ];
+    // Bodies, edges, profiles, the grid and the background: the GPU viewport draws these from
+    // their own tokens; the engine's values are only the headless snapshot's.
+    const NEUTRAL: &[&str] = &["BODY", "BODY_SELECTED", "EDGE", "PROFILE", "GRID", "GRID_MAJOR", "BG_TOP", "BG_BOTTOM", "SECTION_CAP"];
+    let src = include_str!("../../engine/src/view.rs");
+    let start = src.find("pub mod colors {").unwrap_or(0);
+    let block = &src[start..];
+    let block = &block[..block.find("\n}").unwrap_or(block.len())];
+    let mut names: Vec<&str> = block.lines().filter_map(|l| l.trim().strip_prefix("pub const ")).filter_map(|l| l.split(':').next()).collect();
+    names.sort_unstable();
+    let mut placed: Vec<&str> = MAPPED.iter().chain(NEUTRAL).copied().collect();
+    placed.sort_unstable();
+    assert_eq!(names, placed, "an engine colour tag must be mapped to a token in `viewport::sketch_color` or listed as neutral");
+}
diff --git a/crates/ui-egui/src/colour_vision_tests.rs b/crates/ui-egui/src/colour_vision_tests.rs
new file mode 100644
index 00000000..5d5449f4
--- /dev/null
+++ b/crates/ui-egui/src/colour_vision_tests.rs
@@ -0,0 +1,861 @@
+//! Colour vision modes (#778), measured. Colours that appear together must stay apart (CIEDE2000
+//! 10 or more) for normal vision and for the loss each mode is for, with two simulations of that
+//! loss: Machado, Oliveira and Fernandes 2009 (severity 1) and Brettel, Viénot and Mollon 1997.
+//! The instruments are checked first: CIEDE2000 on the 34 pairs Sharma, Wu and Dalal published
+//! with their paper, Brettel on white and its own anchors.
+//!
+//! When a token edit breaks a mode here, give that token a value in the mode's table
+//! (`assets/styles/ui/palettes.rs`) that passes.
+
+use std::collections::BTreeSet;
+
+use egui::Color32;
+use serde_json::json;
+
+use crate::theme::{ColorVision, Tokens};
+
+type Rgb8 = [u8; 3];
+type V3 = [f64; 3];
+type M3 = [[f64; 3]; 3];
+
+/// The smallest difference a pair may have (CIEDE2000).
+const FLOOR: f64 = 10.0;
+/// The shading the analysis colours get in the shader (`lit`: 0.55 turned away, 1 facing the eye).
+const LIT: [f64; 4] = [0.55, 0.7, 0.85, 1.0];
+const MODES: [ColorVision; 3] = [ColorVision::Protan, ColorVision::Deutan, ColorVision::Tritan];
+
+#[derive(Clone, Copy, Debug, PartialEq)]
+enum Eye {
+    Normal,
+    Protan,
+    Deutan,
+    Tritan,
+}
+
+#[derive(Clone, Copy, Debug)]
+enum Instrument {
+    Machado,
+    Brettel,
+}
+
+/// The loss a mode is for.
+fn eye(mode: ColorVision) -> Eye {
+    match mode {
+        ColorVision::Off => Eye::Normal,
+        ColorVision::Protan => Eye::Protan,
+        ColorVision::Deutan => Eye::Deutan,
+        ColorVision::Tritan => Eye::Tritan,
+    }
+}
+
+// ---- the instruments ----
+
+fn to_lin(c: f64) -> f64 {
+    if c <= 0.04045 { c / 12.92 } else { ((c + 0.055) / 1.055).powf(2.4) }
+}
+
+fn to_srgb(c: f64) -> f64 {
+    if c <= 0.0031308 { 12.92 * c } else { 1.055 * c.powf(1.0 / 2.4) - 0.055 }
+}
+
+fn mul(m: &M3, v: V3) -> V3 {
+    [0, 1, 2].map(|r| m[r][0] * v[0] + m[r][1] * v[1] + m[r][2] * v[2])
+}
+
+fn mat(a: &M3, b: &M3) -> M3 {
+    [0, 1, 2].map(|r| [0, 1, 2].map(|c| (0..3).map(|k| a[r][k] * b[k][c]).sum()))
+}
+
+fn inv(m: &M3) -> M3 {
+    let [[a, b, c], [d, e, f], [g, h, i]] = *m;
+    let det = a * (e * i - f * h) - b * (d * i - f * g) + c * (d * h - e * g);
+    [
+        [(e * i - f * h) / det, (c * h - b * i) / det, (b * f - c * e) / det],
+        [(f * g - d * i) / det, (a * i - c * g) / det, (c * d - a * f) / det],
+        [(d * h - e * g) / det, (b * g - a * h) / det, (a * e - b * d) / det],
+    ]
+}
+
+fn cross(u: V3, v: V3) -> V3 {
+    [u[1] * v[2] - u[2] * v[1], u[2] * v[0] - u[0] * v[2], u[0] * v[1] - u[1] * v[0]]
+}
+
+fn dot(u: V3, v: V3) -> f64 {
+    u[0] * v[0] + u[1] * v[1] + u[2] * v[2]
+}
+
+/// Machado, Oliveira, Fernandes 2009, severity 1.0, on linear sRGB (the authors' Table 1).
+fn machado(eye: Eye) -> M3 {
+    match eye {
+        Eye::Protan => [[0.152286, 1.052583, -0.204868], [0.114503, 0.786281, 0.099216], [-0.003882, -0.048116, 1.051998]],
+        Eye::Deutan => [[0.367322, 0.860646, -0.227968], [0.280085, 0.672501, 0.047413], [-0.011820, 0.042940, 0.968881]],
+        Eye::Tritan => [[1.255528, -0.076749, -0.178779], [-0.078411, 0.930809, 0.147602], [0.004733, 0.691367, 0.303900]],
+        Eye::Normal => [[1.0, 0.0, 0.0], [0.0, 1.0, 0.0], [0.0, 0.0, 1.0]],
+    }
+}
+
+/// Linear sRGB to CIE XYZ (D65), IEC 61966-2-1.
+const XYZ_FROM_LIN: M3 = [[0.4124564, 0.3575761, 0.1804375], [0.2126729, 0.7151522, 0.0721750], [0.0193339, 0.1191920, 0.9503041]];
+/// XYZ to cone responses (LMS), Smith and Pokorny 1975.
+const LMS_FROM_XYZ: M3 = [[0.15514, 0.54312, -0.03286], [-0.15514, 0.45684, 0.03286], [0.0, 0.0, 0.00801]];
+/// CIE 1931 2-degree colour matching functions (CIE 018:2019) at Brettel's anchors.
+const CIE_475: V3 = [0.1421, 0.1126, 1.0419];
+const CIE_485: V3 = [0.05795001, 0.1693, 0.6162];
+const CIE_575: V3 = [0.8425, 0.9154, 0.0018];
+const CIE_660: V3 = [0.1649, 0.061, 0.0];
+
+/// The missing cone (0 L, 1 M, 2 S) and the two anchor wavelengths of its half-planes.
+fn anchors(eye: Eye) -> (usize, V3, V3) {
+    match eye {
+        Eye::Protan => (0, CIE_475, CIE_575),
+        Eye::Deutan => (1, CIE_475, CIE_575),
+        Eye::Normal | Eye::Tritan => (2, CIE_485, CIE_660),
+    }
+}
+
+/// Brettel, Viénot, Mollon 1997: the missing cone's response is put back on one of two half-planes
+/// through white and an anchor colour, chosen by the side of the white axis the colour is on.
+fn brettel(eye: Eye, lin: V3) -> V3 {
+    let lms = mat(&LMS_FROM_XYZ, &XYZ_FROM_LIN);
+    let (c, w1, w2) = anchors(eye);
+    let white = mul(&lms, [1.0; 3]);
+    let (a1, a2) = (mul(&LMS_FROM_XYZ, w1), mul(&LMS_FROM_XYZ, w2));
+    let mut axis = [0.0; 3];
+    axis[c] = 1.0;
+    let sep = cross(white, axis);
+    let mut q = mul(&lms, lin);
+    let n = if dot(q, sep) * dot(a1, sep) >= 0.0 { cross(white, a1) } else { cross(white, a2) };
+    q[c] = -(0..3).filter(|k| *k != c).map(|k| n[k] * q[k]).sum::<f64>() / n[c];
+    mul(&inv(&lms), q)
+}
+
+/// What an eye sees of an sRGB colour, as sRGB 0..1.
+fn simulate(c: Rgb8, eye: Eye, how: Instrument) -> V3 {
+    let srgb = c.map(|v| f64::from(v) / 255.0);
+    if eye == Eye::Normal {
+        return srgb;
+    }
+    let lin = srgb.map(to_lin);
+    let out = match how {
+        Instrument::Machado => mul(&machado(eye), lin),
+        Instrument::Brettel => brettel(eye, lin),
+    };
+    out.map(|v| to_srgb(v.clamp(0.0, 1.0)))
+}
+
+/// CIELAB (D65) of an sRGB colour.
+fn lab(srgb: V3) -> V3 {
+    let [x, y, z] = mul(&XYZ_FROM_LIN, srgb.map(to_lin));
+    let f = |t: f64| if t > (6.0f64 / 29.0).powi(3) { t.cbrt() } else { t / (3.0 * (6.0f64 / 29.0).powi(2)) + 4.0 / 29.0 };
+    let (fx, fy, fz) = (f(x / 0.95047), f(y), f(z / 1.08883));
+    [116.0 * fy - 16.0, 500.0 * (fx - fy), 200.0 * (fy - fz)]
+}
+
+/// CIEDE2000 (Sharma, Wu, Dalal 2005).
+fn de2000(l1: V3, l2: V3) -> f64 {
+    let ([lightness1, a1, b1], [lightness2, a2, b2]) = (l1, l2);
+    let (c1, c2) = (a1.hypot(b1), a2.hypot(b2));
+    let cb = (c1 + c2) / 2.0;
+    let g = 0.5 * (1.0 - (cb.powi(7) / (cb.powi(7) + 25f64.powi(7))).sqrt());
+    let (a1p, a2p) = ((1.0 + g) * a1, (1.0 + g) * a2);
+    let (c1p, c2p) = (a1p.hypot(b1), a2p.hypot(b2));
+    let hue = |b: f64, a: f64, c: f64| if c == 0.0 { 0.0 } else { b.atan2(a).to_degrees().rem_euclid(360.0) };
+    let (h1p, h2p) = (hue(b1, a1p, c1p), hue(b2, a2p, c2p));
+    let dlp = lightness2 - lightness1;
+    let dcp = c2p - c1p;
+    let dhp = if c1p * c2p == 0.0 {
+        0.0
+    } else if (h2p - h1p).abs() <= 180.0 {
+        h2p - h1p
+    } else if h2p - h1p > 180.0 {
+        h2p - h1p - 360.0
+    } else {
+        h2p - h1p + 360.0
+    };
+    let dhp_big = 2.0 * (c1p * c2p).sqrt() * (dhp / 2.0).to_radians().sin();
+    let lbp = (lightness1 + lightness2) / 2.0;
+    let cbp = (c1p + c2p) / 2.0;
+    let hbp = if c1p * c2p == 0.0 {
+        h1p + h2p
+    } else if (h1p - h2p).abs() <= 180.0 {
+        (h1p + h2p) / 2.0
+    } else if h1p + h2p < 360.0 {
+        (h1p + h2p + 360.0) / 2.0
+    } else {
+        (h1p + h2p - 360.0) / 2.0
+    };
+    let cos = |deg: f64| deg.to_radians().cos();
+    let t = 1.0 - 0.17 * cos(hbp - 30.0) + 0.24 * cos(2.0 * hbp) + 0.32 * cos(3.0 * hbp + 6.0) - 0.20 * cos(4.0 * hbp - 63.0);
+    let dtheta = 30.0 * (-((hbp - 275.0) / 25.0).powi(2)).exp();
+    let rc = 2.0 * (cbp.powi(7) / (cbp.powi(7) + 25f64.powi(7))).sqrt();
+    let sl = 1.0 + 0.015 * (lbp - 50.0).powi(2) / (20.0 + (lbp - 50.0).powi(2)).sqrt();
+    let sc = 1.0 + 0.045 * cbp;
+    let sh = 1.0 + 0.015 * cbp * t;
+    let rt = -(2.0 * dtheta).to_radians().sin() * rc;
+    ((dlp / sl).powi(2) + (dcp / sc).powi(2) + (dhp_big / sh).powi(2) + rt * (dcp / sc) * (dhp_big / sh)).sqrt()
+}
+
+fn diff(a: Rgb8, b: Rgb8, eye: Eye, how: Instrument) -> f64 {
+    de2000(lab(simulate(a, eye, how)), lab(simulate(b, eye, how)))
+}
+
+fn normal(a: Rgb8, b: Rgb8) -> f64 {
+    diff(a, b, Eye::Normal, Instrument::Machado)
+}
+
+/// The smallest difference for normal vision and for the mode's loss (both instruments).
+fn worst(mode: ColorVision, a: Rgb8, b: Rgb8) -> f64 {
+    let e = eye(mode);
+    normal(a, b).min(diff(a, b, e, Instrument::Machado)).min(diff(a, b, e, Instrument::Brettel))
+}
+
+// ---- the colours that appear together ----
+
+fn rgb(c: Color32) -> Rgb8 {
+    [c.r(), c.g(), c.b()]
+}
+
+/// A translucent colour over an opaque ground, in sRGB (close to egui's blend).
+fn over(c: Color32, ground: Color32) -> Rgb8 {
+    let [r, g, b, a] = c.to_srgba_unmultiplied();
+    let k = f64::from(a) / 255.0;
+    let mix = |f: u8, g: u8| (f64::from(f) * k + f64::from(g) * (1.0 - k)).round() as u8;
+    [mix(r, ground.r()), mix(g, ground.g()), mix(b, ground.b())]
+}
+
+/// An analysis colour as the shader shades it.
+fn lit(c: [f32; 3], k: f64) -> Rgb8 {
+    c.map(|x| ((f64::from(x) * 255.0).round() * k).min(255.0).round() as u8)
+}
+
+struct Group {
+    name: &'static str,
+    /// Colours that must differ from each other.
+    members: Vec<(&'static str, Rgb8)>,
+    /// What they are drawn on.
+    grounds: Vec<(&'static str, Rgb8)>,
+}
+
+fn group(name: &'static str, members: &[(&'static str, Color32)], grounds: &[(&'static str, Color32)]) -> Group {
+    for (n, c) in members.iter().chain(grounds) {
+        assert_eq!(c.a(), 255, "{name}: {n} is translucent; put it over its ground first");
+    }
+    Group { name, members: members.iter().map(|(n, c)| (*n, rgb(*c))).collect(), grounds: grounds.iter().map(|(n, c)| (*n, rgb(*c))).collect() }
+}
+
+/// Every group of meaning-carrying colours that appear together (and the icons' colours, drawn on
+/// the toolbar with their caller's ink, fill and accent). Each colour is named by its `Tokens`
+/// field, so `every_token_is_measured_or_carries_no_meaning` knows which tokens are measured.
+fn groups(t: &Tokens) -> Vec<Group> {
+    let lift = |c: Color32| {
+        Color32::from_rgb(c.r().saturating_add(t.hover_face_lift), c.g().saturating_add(t.hover_face_lift), c.b().saturating_add(t.hover_face_lift))
+    };
+    let ic = &t.icons;
+    let a = &t.analysis;
+    let mut out = vec![
+        group(
+            "sketch lines",
+            &[
+                ("sketch", t.sketch),
+                ("sketch_fixed", t.sketch_fixed),
+                ("sketch_locked", t.sketch_locked),
+                ("sketch_projected", t.sketch_projected),
+                ("sketch_lost", t.sketch_lost),
+                ("sketch_construction", t.sketch_construction),
+                ("sketch_centerline", t.sketch_centerline),
+                ("preview_sketch", t.preview_sketch),
+            ],
+            &[("viewport_top", t.viewport_top), ("viewport_bottom", t.viewport_bottom)],
+        ),
+        group(
+            "sketch points",
+            &[("sketch_point", t.sketch_point), ("sketch_point_free", t.sketch_point_free), ("sketch_locked", t.sketch_locked)],
+            &[("viewport_top", t.viewport_top)],
+        ),
+        group(
+            "timeline",
+            &[("timeline_item", t.timeline_item), ("timeline_item_error", t.timeline_item_error), ("hover", t.hover), ("accent_soft", t.accent_soft)],
+            &[],
+        ),
+        group("UI text", &[("error", t.error), ("warning", t.warning), ("text", t.text)], &[("panel", t.panel)]),
+        group("origin axes", &[("axis_x", t.axis_x), ("axis_y", t.axis_y), ("axis_z", t.axis_z)], &[("viewport_top", t.viewport_top)]),
+        group("view triad", &[("triad[0]", t.triad[0]), ("triad[1]", t.triad[1]), ("triad[2]", t.triad[2])], &[("viewport_top", t.viewport_top)]),
+        group("gizmo", &[("gizmo[0]", t.gizmo[0]), ("gizmo[1]", t.gizmo[1]), ("gizmo[2]", t.gizmo[2])], &[("viewport_top", t.viewport_top)]),
+        group("bend lines", &[("bend_up", t.bend_up), ("bend_down", t.bend_down)], &[("viewport_top", t.viewport_top)]),
+        group("box select", &[("box_window", t.box_window), ("box_crossing", t.box_crossing)], &[("viewport_top", t.viewport_top)]),
+        group(
+            "selection",
+            &[
+                ("body", t.body),
+                ("sel_face", t.sel_face),
+                ("body_selected", t.body_selected),
+                ("hover_face_lift", lift(t.body)),
+                ("preview_add", t.preview_add),
+            ],
+            &[],
+        ),
+        group("section", &[("section_cap", t.section_cap)], &[("body", t.body)]),
+        group("interference", &[("interference", t.interference)], &[("body", t.body)]),
+        // The scale's three stops, unlit. Shaded (a stop at one angle to the light, the next at
+        // another), middle and tight merge for a red-green loss (3.3 protan, 5.2 deutan) and flat
+        // and middle for tritan (4.6). That is the scale's own fault, in Off too: #975.
+        group(
+            "curvature map",
+            &[
+                ("analysis.curvature[0]", crate::theme::srgb(a.curvature[0])),
+                ("analysis.curvature[1]", crate::theme::srgb(a.curvature[1])),
+                ("analysis.curvature[2]", crate::theme::srgb(a.curvature[2])),
+            ],
+            &[],
+        ),
+        group(
+            "ribbon accents",
+            &[("glyph_text", t.glyph_text), ("sketch_accent", t.sketch_accent), ("construction_geom", t.construction_geom)],
+            &[("toolbar", t.toolbar)],
+        ),
+        group(
+            "origin icon",
+            &[("icons.axes[0]", ic.axes[0]), ("icons.axes[1]", ic.axes[1]), ("icons.axes[2]", ic.axes[2])],
+            &[("toolbar", t.toolbar)],
+        ),
+        group(
+            "accessibility icon",
+            &[("icons.access[0]", ic.access[0]), ("icons.access[1]", ic.access[1]), ("icon_fill", t.icon_fill), ("icon", t.icon)],
+            &[],
+        ),
+        group("draft icon", &[("icons.draft[0]", ic.draft[0]), ("icons.draft[1]", ic.draft[1]), ("icon", t.icon)], &[]),
+        group(
+            "curvature icon",
+            &[("icons.curvature[0]", ic.curvature[0]), ("icons.curvature[1]", ic.curvature[1]), ("icons.curvature[2]", ic.curvature[2])],
+            &[],
+        ),
+        group(
+            "appearance icon",
+            &[("icons.paint[0]", ic.paint[0]), ("icons.paint[1]", ic.paint[1]), ("icons.paint[2]", ic.paint[2]), ("icon_fill", t.icon_fill)],
+            &[],
+        ),
+        group("environment icon", &[("icons.sky", ic.sky), ("icons.floor", ic.floor), ("icons.highlight", ic.highlight)], &[]),
+        group("warning icon", &[("icons.warning", ic.warning), ("icon", t.icon)], &[("toolbar", t.toolbar)]),
+        group("interference icon", &[("icons.interference", ic.interference), ("icon", t.icon)], &[("toolbar", t.toolbar)]),
+        group("folder icons", &[("icons.folder", ic.folder), ("icons.plane", ic.plane), ("icons.fold", ic.fold), ("icon", t.icon)], &[]),
+        group("sheet icons", &[("icons.sheet", ic.sheet), ("icons.sheet_2", ic.sheet_2), ("icon", t.icon)], &[]),
+        group(
+            "app bar buttons",
+            &[("app_bar_icon[0]", t.app_bar_icon[0]), ("app_bar_icon[1]", t.app_bar_icon[1]), ("app_bar_icon[2]", t.app_bar_icon[2])],
+            &[("app_bar", t.app_bar)],
+        ),
+        group("logo", &[("logo[0]", t.logo[0]), ("logo[1]", t.logo[1]), ("logo[2]", t.logo[2])], &[("app_bar", t.app_bar)]),
+    ];
+    // The removed part of a cut preview is translucent over the body.
+    if let Some(sel) = out.iter_mut().find(|g| g.name == "selection") {
+        sel.members.push(("preview_cut", over(t.preview_cut, t.body)));
+    }
+    out
+}
+
+/// Measured by the shaded check in `every_mode_keeps_colours_apart_for_its_eye`.
+const SHADED: [&str; 2] = ["analysis.draft", "analysis.access"];
+
+/// Tokens no colour vision mode needs to keep apart, and why. A new token fails
+/// `every_token_is_measured_or_carries_no_meaning` until it is in a group above or here.
+const NO_MEANING: &[(&str, &str)] = &[
+    // The window's chrome: grounds, text and borders (measured as grounds where meaning sits on them).
+    ("panel_header", "chrome"),
+    ("border", "chrome"),
+    ("text_dim", "secondary text"),
+    ("accent", "the one interface accent"),
+    ("timeline", "the timeline's ground"),
+    ("dialog_bg", "chrome"),
+    ("dialog_border", "chrome"),
+    ("chip", "a label's ground"),
+    ("heading_bg", "chrome"),
+    ("subheading_bg", "chrome"),
+    ("overlay", "a chip's ground over the view"),
+    ("app_bar_text", "text"),
+    ("app_bar_hover", "a hovered tab, translucent white"),
+    ("app_bar_tab_edge", "an inactive tab's outline, translucent white"),
+    ("timeline_marker", "the rollback marker, alone"),
+    ("field", "a field's ground"),
+    // Highlights: shades of the accent blue over what they mark, by design close to each other.
+    ("sel_edge", "selection highlight"),
+    ("sel_edge_rim", "selection highlight"),
+    ("hover_edge", "hover highlight"),
+    ("hover_edge_halo", "hover highlight"),
+    ("sel_profile", "selection highlight"),
+    ("sel_profile_edge", "selection highlight"),
+    ("hover_profile", "hover highlight"),
+    ("hover_profile_edge", "hover highlight"),
+    ("sel_vertex", "selection highlight"),
+    ("rubber_band", "the shape being drawn"),
+    ("manipulator", "a drag handle, alone"),
+    // Planes, points, the grid and the model's edges: one neutral each, told apart by shape.
+    ("origin_plane", "a plane, told apart by its place"),
+    ("origin_plane_edge", "a plane's edge"),
+    ("origin_plane_hover", "hover highlight"),
+    ("origin_point", "the origin, alone"),
+    ("construction_plane", "a plane"),
+    ("body_edge", "the model's edges"),
+    ("grid", "the grid"),
+    ("grid_major", "the grid"),
+    ("profile_fill", "a closed profile's tint"),
+    ("dimension", "dimension text"),
+    ("dimension_driven", "dimension text, dimmed"),
+    ("glyph_bg", "a constraint glyph's ground"),
+    ("glyph_edge", "a constraint glyph's edge"),
+    // The navigation cube: labelled faces.
+    ("cube_face", "labelled"),
+    ("cube_border", "labelled"),
+    ("cube_text", "labelled"),
+    ("cube_hover", "hover highlight"),
+    // Not a colour, or the end of a mark that is measured elsewhere.
+    ("analysis.hatch", "a flag: stripes on the failing faces"),
+    ("logo[3]", "the mark's white edge"),
+    // Icon colours that are a shade of a measured one, or one mark alone.
+    ("icons.sheet_light", "a lighter shade of a sheet"),
+    ("icons.sheet_line", "lines on a sheet"),
+    ("icons.glint", "a highlight"),
+    ("icons.stripe", "zebra stripes, grey"),
+    ("icons.agent", "the agent's pointer, alone"),
+    ("icons.marker_halo", "a dark halo under a marker"),
+];
+
+/// Every token field, by path (`sketch`, `analysis.draft`, `logo[3]`…): the arrays of distinct
+/// meanings by element where only some elements are measured.
+fn token_fields(t: &Tokens) -> BTreeSet<String> {
+    let text = format!("{t:#?}");
+    let mut out = BTreeSet::new();
+    let mut parent: Option<String> = None;
+    for line in text.lines() {
+        let indent = line.len() - line.trim_start().len();
+        let Some((name, rest)) = line.trim_start().split_once(": ") else { continue };
+        match indent {
+            4 if rest.ends_with('{') => parent = Some(name.to_string()),
+            4 => {
+                parent = None;
+                out.insert(name.to_string());
+            }
+            8 => {
+                if let Some(p) = &parent {
+                    out.insert(format!("{p}.{name}"));
+                }
+            }
+            _ => {}
+        }
+    }
+    out
+}
+
+/// A group member's token field (`triad[0]` is part of `triad`).
+fn field_of(name: &str) -> &str {
+    name.split('[').next().unwrap_or(name)
+}
+
+#[test]
+fn every_token_is_measured_or_carries_no_meaning() {
+    for t in [Tokens::light(), Tokens::dark()] {
+        let measured: BTreeSet<&str> =
+            groups(&t).iter().flat_map(|g| g.members.iter().chain(&g.grounds).map(|(n, _)| field_of(n))).chain(SHADED).collect();
+        // An element of an array (`logo[3]`) is listed for the record; its array is measured.
+        let listed: BTreeSet<&str> = NO_MEANING.iter().map(|(n, _)| field_of(n)).collect();
+        let fields = token_fields(&t);
+        let unplaced: Vec<&String> = fields.iter().filter(|f| !measured.contains(f.as_str()) && !listed.contains(f.as_str())).collect();
+        assert!(unplaced.is_empty(), "tokens neither measured (`groups`) nor listed in `NO_MEANING`: {unplaced:?}");
+        let stale: Vec<&&str> = measured.iter().chain(&listed).filter(|f| !fields.contains(**f)).collect();
+        assert!(stale.is_empty(), "names that are not token fields: {stale:?}");
+        let both: Vec<&str> = NO_MEANING.iter().map(|(n, _)| *n).filter(|n| !n.contains('[') && measured.contains(n)).collect();
+        assert!(both.is_empty(), "measured and also listed as carrying no meaning: {both:?}");
+    }
+}
+
+/// Every pair in the groups: (group, name a, a, name b, b).
+fn pairs(t: &Tokens) -> Vec<(String, Rgb8, Rgb8)> {
+    let mut out = Vec::new();
+    for g in groups(t) {
+        for (i, (na, a)) in g.members.iter().enumerate() {
+            for (nb, b) in g.members.iter().skip(i + 1).chain(&g.grounds) {
+                out.push((format!("{}: {na} vs {nb}", g.name), *a, *b));
+            }
+        }
+    }
+    out
+}
+
+/// Pairs under the floor that the tables leave as they are (decided for #778). Each is close to
+/// the floor for normal vision too, and construction and centerline lines also differ by their
+/// dash patterns.
+fn left_as_they_are(mode: ColorVision, dark: bool) -> BTreeSet<String> {
+    let mut v = vec!["sketch lines: sketch_construction vs sketch_centerline"];
+    if mode == ColorVision::Tritan {
+        v.push("sketch lines: sketch_lost vs sketch_centerline");
+        v.push(if dark { "timeline: hover vs accent_soft" } else { "timeline: timeline_item vs accent_soft" });
+        v.push("selection: sel_face vs preview_add");
+    }
+    v.into_iter().map(String::from).collect()
+}
+
+// ---- the tests ----
+
+/// Sharma, Wu, Dalal, "The CIEDE2000 Color-Difference Formula: Implementation Notes,
+/// Supplementary Test Data, and Mathematical Observations", Color Research and Application 30
+/// (2005), Table 1: L*, a*, b* of each pair, then the difference.
+const SHARMA: [[f64; 7]; 34] = [
+    [50.0000, 2.6772, -79.7751, 50.0000, 0.0000, -82.7485, 2.0425],
+    [50.0000, 3.1571, -77.2803, 50.0000, 0.0000, -82.7485, 2.8615],
+    [50.0000, 2.8361, -74.0200, 50.0000, 0.0000, -82.7485, 3.4412],
+    [50.0000, -1.3802, -84.2814, 50.0000, 0.0000, -82.7485, 1.0000],
+    [50.0000, -1.1848, -84.8006, 50.0000, 0.0000, -82.7485, 1.0000],
+    [50.0000, -0.9009, -85.5211, 50.0000, 0.0000, -82.7485, 1.0000],
+    [50.0000, 0.0000, 0.0000, 50.0000, -1.0000, 2.0000, 2.3669],
+    [50.0000, -1.0000, 2.0000, 50.0000, 0.0000, 0.0000, 2.3669],
+    [50.0000, 2.4900, -0.0010, 50.0000, -2.4900, 0.0009, 7.1792],
+    [50.0000, 2.4900, -0.0010, 50.0000, -2.4900, 0.0010, 7.1792],
+    [50.0000, 2.4900, -0.0010, 50.0000, -2.4900, 0.0011, 7.2195],
+    [50.0000, 2.4900, -0.0010, 50.0000, -2.4900, 0.0012, 7.2195],
+    [50.0000, -0.0010, 2.4900, 50.0000, 0.0009, -2.4900, 4.8045],
+    [50.0000, -0.0010, 2.4900, 50.0000, 0.0010, -2.4900, 4.8045],
+    [50.0000, -0.0010, 2.4900, 50.0000, 0.0011, -2.4900, 4.7461],
+    [50.0000, 2.5000, 0.0000, 50.0000, 0.0000, -2.5000, 4.3065],
+    [50.0000, 2.5000, 0.0000, 73.0000, 25.0000, -18.0000, 27.1492],
+    [50.0000, 2.5000, 0.0000, 61.0000, -5.0000, 29.0000, 22.8977],
+    [50.0000, 2.5000, 0.0000, 56.0000, -27.0000, -3.0000, 31.9030],
+    [50.0000, 2.5000, 0.0000, 58.0000, 24.0000, 15.0000, 19.4535],
+    [50.0000, 2.5000, 0.0000, 50.0000, 3.1736, 0.5854, 1.0000],
+    [50.0000, 2.5000, 0.0000, 50.0000, 3.2972, 0.0000, 1.0000],
+    [50.0000, 2.5000, 0.0000, 50.0000, 1.8634, 0.5757, 1.0000],
+    [50.0000, 2.5000, 0.0000, 50.0000, 3.2592, 0.3350, 1.0000],
+    [60.2574, -34.0099, 36.2677, 60.4626, -34.1751, 39.4387, 1.2644],
+    [63.0109, -31.0961, -5.8663, 62.8187, -29.7946, -4.0864, 1.2630],
+    [61.2901, 3.7196, -5.3901, 61.4292, 2.2480, -4.9620, 1.8731],
+    [35.0831, -44.1164, 3.7933, 35.0232, -40.0716, 1.5901, 1.8645],
+    [22.7233, 20.0904, -46.6940, 23.0331, 14.9730, -42.5619, 2.0373],
+    [36.4612, 47.8580, 18.3852, 36.2715, 50.5065, 21.2231, 1.4146],
+    [90.8027, -2.0831, 1.4410, 91.1528, -1.6435, 0.0447, 1.4441],
+    [90.9257, -0.5406, -0.9208, 88.6381, -0.8985, -0.7239, 1.5381],
+    [6.7747, -0.2908, -2.4247, 5.8714, -0.0985, -2.2286, 0.6377],
+    [2.0776, 0.0795, -1.1350, 0.9033, -0.0636, -0.5514, 0.9082],
+];
+
+#[test]
+fn ciede2000_reproduces_sharmas_test_pairs() {
+    for (i, p) in SHARMA.iter().enumerate() {
+        let got = de2000([p[0], p[1], p[2]], [p[3], p[4], p[5]]);
+        assert!((got - p[6]).abs() < 1e-4, "pair {}: {got}, published {}", i + 1, p[6]);
+        // The formula is symmetric.
+        assert!((de2000([p[3], p[4], p[5]], [p[0], p[1], p[2]]) - got).abs() < 1e-9, "pair {}", i + 1);
+    }
+}
+
+#[test]
+fn the_simulations_keep_white_and_brettels_anchors() {
+    let lms = mat(&LMS_FROM_XYZ, &XYZ_FROM_LIN);
+    for e in [Eye::Protan, Eye::Deutan, Eye::Tritan] {
+        let w = brettel(e, [1.0; 3]);
+        assert!(w.iter().all(|v| (v - 1.0).abs() < 1e-9), "{e:?}: white -> {w:?}");
+        let (_, a1, a2) = anchors(e);
+        for a in [a1, a2] {
+            let lin = mul(&inv(&lms), mul(&LMS_FROM_XYZ, a));
+            let back = brettel(e, lin);
+            assert!(lin.iter().zip(back).all(|(x, y)| (x - y).abs() < 1e-9), "{e:?}: anchor {lin:?} -> {back:?}");
+        }
+        let m = machado(e);
+        assert!(m.iter().all(|row| (row.iter().sum::<f64>() - 1.0).abs() < 1e-5), "{e:?}: Machado keeps white");
+    }
+    // Known losses: pure red and green merge for a red-green loss, blue and green for a blue one.
+    let (red, green, blue) = ([220, 60, 60], [60, 170, 60], [60, 100, 230]);
+    assert!(normal(red, green) > 60.0);
+    for how in [Instrument::Machado, Instrument::Brettel] {
+        assert!(diff(red, green, Eye::Deutan, how) < 10.0, "{how:?}");
+        assert!(diff(blue, green, Eye::Tritan, how) < diff(blue, green, Eye::Normal, how), "{how:?}");
+    }
+}
+
+#[test]
+fn off_gives_the_theme_unchanged() {
+    assert_eq!(Tokens::themed(false, ColorVision::Off), Tokens::light());
+    assert_eq!(Tokens::themed(true, ColorVision::Off), Tokens::dark());
+    for dark in [false, true] {
+        assert!(!Tokens::themed(dark, ColorVision::Off).analysis.hatch);
+        // Protan and Deutan share the red-green table.
+        assert_eq!(Tokens::themed(dark, ColorVision::Protan), Tokens::themed(dark, ColorVision::Deutan));
+    }
+}
+
+/// The token fields whose `Debug` text differs (`triad`, `analysis.draft`…), so a field cannot
+/// change in a mode by accident.
+fn changed_fields(a: &Tokens, b: &Tokens) -> BTreeSet<String> {
+    let (la, lb) = (format!("{a:#?}"), format!("{b:#?}"));
+    let (la, lb): (Vec<&str>, Vec<&str>) = (la.lines().collect(), lb.lines().collect());
+    assert_eq!(la.len(), lb.len());
+    let mut out = BTreeSet::new();
+    for i in (0..la.len()).filter(|i| la[*i] != lb[*i]) {
+        // The named fields above this line, innermost first, up to a field of `Tokens`.
+        let mut path = Vec::new();
+        let mut indent = usize::MAX;
+        for line in la[..=i].iter().rev() {
+            let here = line.len() - line.trim_start().len();
+            if here < indent
+                && let Some((name, _)) = line.trim_start().split_once(':')
+                && name.chars().all(|c| c.is_ascii_lowercase() || c.is_ascii_digit() || c == '_')
+            {
+                path.push(name.to_string());
+                indent = here;
+            }
+            if indent <= 4 {
+                break;
+            }
+        }
+        path.reverse();
+        out.insert(path.join("."));
+    }
+    out
+}
+
+#[test]
+fn each_mode_changes_only_its_table() {
+    let set = |s: &[&str]| s.iter().map(|x| x.to_string()).collect::<BTreeSet<_>>();
+    let red_green_both = [
+        "triad",
+        "gizmo",
+        "analysis.draft",
+        "analysis.access",
+        "analysis.hatch",
+        "icons.axes",
+        "icons.access",
+        "icons.draft",
+        "bend_up",
+        "bend_down",
+        "sketch_accent",
+        "preview_sketch",
+    ];
+    let mut red_green_light = red_green_both.to_vec();
+    red_green_light.extend(["sketch_projected", "sketch_locked", "timeline_item_error"]);
+    for (dark, mode, want) in [
+        (false, ColorVision::Protan, set(&red_green_light)),
+        (true, ColorVision::Protan, set(&red_green_both)),
+        (false, ColorVision::Deutan, set(&red_green_light)),
+        (true, ColorVision::Deutan, set(&red_green_both)),
+        (false, ColorVision::Tritan, set(&["sketch_locked", "box_crossing", "preview_sketch", "analysis.hatch"])),
+        (true, ColorVision::Tritan, set(&["sketch_locked", "box_crossing", "glyph_text", "preview_sketch", "analysis.hatch"])),
+    ] {
+        let base = Tokens::themed(dark, ColorVision::Off);
+        assert_eq!(changed_fields(&base, &Tokens::themed(dark, mode)), want, "{mode:?}, dark {dark}");
+    }
+}
+
+#[test]
+fn every_mode_keeps_colours_apart_for_its_eye() {
+    let mut report = Vec::new();
+    for dark in [false, true] {
+        let off = Tokens::themed(dark, ColorVision::Off);
+        for mode in MODES {
+            let on = Tokens::themed(dark, mode);
+            let mut left = BTreeSet::new();
+            for ((name, a0, b0), (_, a1, b1)) in pairs(&off).into_iter().zip(pairs(&on)) {
+                // Close for everybody by design (hover tints, a shade of one hue), and not changed
+                // by the mode: not a colour vision fault.
+                if normal(a0, b0) < FLOOR && (a0, b0) == (a1, b1) {
+                    continue;
+                }
+                let w = worst(mode, a1, b1);
+                if w < FLOOR {
+                    report.push(format!("{mode:?} dark={dark} {name}: {w:.1} (before {:.1})", worst(mode, a0, b0)));
+                    left.insert(name);
+                }
+            }
+            assert_eq!(left, left_as_they_are(mode, dark), "{mode:?}, dark {dark}: {report:#?}");
+            // Draft and Accessibility, for faces at any angle to the light against each other.
+            let a = &on.analysis;
+            let shaded = [(a.draft[0], a.draft[1]), (a.draft[0], a.draft[2]), (a.draft[1], a.draft[2]), (a.access[0], a.access[1])];
+            for (p, q) in shaded {
+                for x in LIT {
+                    for y in LIT {
+                        let w = worst(mode, lit(p, x), lit(q, y));
+                        assert!(w >= FLOOR, "{mode:?}, dark {dark}: {p:?} lit {x} vs {q:?} lit {y}: {w:.1}");
+                    }
+                }
+            }
+        }
+    }
+}
+
+#[test]
+fn the_shader_gets_the_modes_colours_and_its_stripes() {
+    for dark in [false, true] {
+        let off = crate::gpu::analysis_colors(&Tokens::themed(dark, ColorVision::Off).analysis);
+        assert_eq!(off[32], 0.0, "no stripes in Off");
+        for mode in MODES {
+            let t = Tokens::themed(dark, mode);
+            let v = crate::gpu::analysis_colors(&t.analysis);
+            assert_eq!(v[32], 1.0, "{mode:?}: stripes on the bad faces");
+            assert_eq!(v[..3], t.analysis.draft[0], "{mode:?}");
+            assert_eq!(v[16..19], t.analysis.access[1], "{mode:?}");
+        }
+    }
+}
+
+// ---- the preference ----
+
+/// Every message the Colour vision section shows (the heading, the mode names and their
+/// tooltips, the sample's names and the note) is in every catalogue, translated: in Japanese,
+/// Korean, Russian and Chinese none is the English text. (German keeps "Protan", "Deutan" and
+/// "Tritan".)
+#[test]
+fn the_sections_messages_are_in_every_catalog() {
+    let load = |text: &str| -> serde_json::Map<String, serde_json::Value> { serde_json::from_str(text).unwrap() };
+    let english = load(include_str!("../../../assets/locales/en.json"));
+    let ids: Vec<&str> = ColorVision::ALL
+        .into_iter()
+        .flat_map(|m| [m.label_id(), m.help_id()])
+        .chain(crate::prefs::COLOUR_VISION_SAMPLE)
+        .chain(["ui.colour_vision", "ui.colour_vision_mode", "ui.colour_vision_sample", "ui.colour_vision_note"])
+        .collect();
+    for (lang, text) in [
+        ("de", include_str!("../../../assets/locales/de.json")),
+        ("ja", include_str!("../../../assets/locales/ja.json")),
+        ("ko", include_str!("../../../assets/locales/ko.json")),
+        ("ru", include_str!("../../../assets/locales/ru.json")),
+        ("zh", include_str!("../../../assets/locales/zh.json")),
+    ] {
+        let catalog = load(text);
+        for id in &ids {
+            let (Some(en), Some(here)) = (english.get(*id), catalog.get(*id)) else {
+                panic!("{lang}: missing message {id} (English: {})", english.contains_key(*id));
+            };
+            assert!(lang == "de" || here != en, "{lang}: {id} is the English text {en}");
+        }
+    }
+}
+
+fn app() -> crate::SolveApp {
+    crate::SolveApp::new(solidcraft_engine::Session::default(), crate::Services::default())
+}
+
+#[test]
+fn saved_preferences_load_the_mode_and_a_bad_one_loads_as_off() {
+    use crate::prefs::Prefs;
+    // Saved before the mode existed.
+    let old: Prefs = serde_json::from_value(json!({"theme": "light"})).unwrap();
+    assert_eq!((old.color_vision, old.theme.as_str()), (ColorVision::Off, "light"));
+    for mode in ColorVision::ALL {
+        let p = Prefs { color_vision: mode, ..Prefs::default() };
+        let v = serde_json::to_value(&p).unwrap();
+        assert_eq!(v["color_vision"], mode.id());
+        assert_eq!(serde_json::from_value::<Prefs>(v).unwrap(), p);
+    }
+    // A value this version doesn't know (a later SolidCraft's mode, a hand edit) is Off, and the
+    // rest of the preferences still load.
+    for bad in [json!("achromat"), json!("PROTAN"), json!(""), json!(3), json!(null), json!(true), json!({"protan": 1}), json!(["tritan"])] {
+        let p: Prefs = serde_json::from_value(json!({"theme": "light", "color_vision": bad})).unwrap();
+        assert_eq!((p.color_vision, p.theme.as_str()), (ColorVision::Off, "light"), "{bad}");
+    }
+}
+
+#[test]
+fn ui_prefs_sets_each_mode_and_refuses_anything_else() {
+    let mut app = app();
+    for mode in ColorVision::ALL {
+        let out = crate::prefs::set(&mut app, &json!({"color_vision": mode.id()})).unwrap();
+        assert_eq!(out["color_vision"], mode.id());
+        assert_eq!(app.preferences.color_vision, mode);
+    }
+    let long = "p".repeat(1 << 20);
+    for bad in [
+        json!("purple"),
+        json!("Protan"),
+        json!(" protan"),
+        json!(""),
+        json!(long),
+        json!(2),
+        json!(-1.5),
+        json!(null),
+        json!(false),
+        json!([]),
+        json!({}),
+    ] {
+        let before = app.preferences.clone();
+        let err = crate::prefs::set(&mut app, &json!({"color_vision": bad, "theme": "light"})).unwrap_err();
+        assert!(err.contains("off, protan, deutan or tritan"), "{err}");
+        assert_eq!(app.preferences, before, "a refused value changes nothing");
+    }
+}
+
+/// Random values (fixed seed): strings near the four ids and far from them, numbers, nesting.
+/// `ui.prefs` takes exactly the four ids and refuses the rest without a change; saved
+/// preferences load every value, unknown ones as Off. Nothing panics.
+#[test]
+fn random_values_never_panic_and_only_the_four_ids_are_taken() {
+    fn value(next: &mut impl FnMut() -> u64, depth: u32) -> serde_json::Value {
+        let ids = ["off", "protan", "deutan", "tritan"];
+        match next() % if depth > 3 { 6 } else { 8 } {
+            0 => json!(ids[(next() % 4) as usize]),
+            1 => {
+                // A near miss: one id with a character changed, added or taken away.
+                let mut s: Vec<char> = ids[(next() % 4) as usize].chars().collect();
+                let i = (next() % s.len() as u64) as usize;
+                match next() % 3 {
+                    0 => s[i] = char::from_u32((next() % 0x2FFF) as u32).unwrap_or('?'),
+                    1 => s.insert(i, ['\0', ' ', 'É', '\u{301}', 'ـ'][(next() % 5) as usize]),
+                    _ => {
+                        s.remove(i);
+                    }
+                }
+                json!(s.into_iter().collect::<String>())
+            }
+            2 => json!((0..next() % 40).map(|_| char::from_u32((next() % 0x10FFFF) as u32).unwrap_or('x')).collect::<String>()),
+            3 => json!(next() as i64),
+            4 => json!(Some(f64::from_bits(next())).filter(|x| x.is_finite()).unwrap_or(0.5)),
+            5 => [json!(null), json!(true), json!(false)][(next() % 3) as usize].clone(),
+            6 => json!((0..next() % 4).map(|_| value(next, depth + 1)).collect::<Vec<_>>()),
+            _ => json!({"color_vision": value(next, depth + 1)}),
+        }
+    }
+    let mut seed = 0x9E37_79B9_7F4A_7C15u64;
+    let mut next = move || {
+        seed ^= seed << 13;
+        seed ^= seed >> 7;
+        seed ^= seed << 17;
+        seed
+    };
+    let mut app = app();
+    let mut taken = 0;
+    for _ in 0..4000 {
+        let v = value(&mut next, 0);
+        let id = v.as_str().and_then(ColorVision::from_id);
+        let before = app.preferences.clone();
+        match crate::prefs::set(&mut app, &json!({"color_vision": v})) {
+            Ok(_) => {
+                taken += 1;
+                assert_eq!(Some(app.preferences.color_vision), id, "{v}");
+            }
+            Err(e) => {
+                assert!(id.is_none() && e.contains("off, protan, deutan or tritan"), "{v}: {e}");
+                assert_eq!(app.preferences, before, "{v}");
+            }
+        }
+        let saved: crate::prefs::Prefs = serde_json::from_value(json!({"theme": "light", "color_vision": v})).unwrap();
+        assert_eq!((saved.color_vision, saved.theme.as_str()), (id.unwrap_or_default(), "light"), "{v}");
+    }
+    assert!(taken > 200, "the four ids came up {taken} times");
+}
+
+#[test]
+fn cancel_puts_the_mode_back_ok_keeps_it_and_restore_defaults_resets_graphics_only() {
+    let mut app = app();
+    let control = |app: &mut crate::SolveApp, p: serde_json::Value| crate::prefs::control(app, &p).unwrap();
+    control(&mut app, json!({"open": "Graphics"}));
+    control(&mut app, json!({"color_vision": "protan"}));
+    assert_eq!(app.preferences.color_vision, ColorVision::Protan);
+    control(&mut app, json!({"button": "cancel"}));
+    assert_eq!(app.preferences.color_vision, ColorVision::Off);
+    control(&mut app, json!({"open": "Graphics"}));
+    control(&mut app, json!({"color_vision": "tritan", "button": "ok"}));
+    assert_eq!(app.preferences.color_vision, ColorVision::Tritan);
+    // Restore Defaults on another page leaves it.
+    control(&mut app, json!({"open": "General"}));
+    control(&mut app, json!({"button": "defaults"}));
+    assert_eq!(app.preferences.color_vision, ColorVision::Tritan);
+    control(&mut app, json!({"open": "Graphics"}));
+    control(&mut app, json!({"button": "defaults"}));
+    assert_eq!(app.preferences.color_vision, ColorVision::Off);
+    control(&mut app, json!({"button": "ok"}));
+}
diff --git a/crates/ui-egui/src/control.rs b/crates/ui-egui/src/control.rs
index 7f5f5f6d..2a180663 100644
--- a/crates/ui-egui/src/control.rs
+++ b/crates/ui-egui/src/control.rs
@@ -630,14 +630,14 @@ fn dispatch(app: &mut SolveApp, ctx: &egui::Context, method: &str, p: &Value) ->
         "ui.render" => {
             let w = f("width").unwrap_or(1280.0).clamp(16.0, 8192.0) as usize;
             let h = f("height").unwrap_or(800.0).clamp(16.0, 8192.0) as usize;
-            // In the window's theme, and cut by the section the viewport shows (an open Section
+            // In the window's theme and colour vision mode, and cut by the section the viewport shows (an open Section
             // Analysis dialog's preview, a sketch's Slice), not only the committed one.
             let scene = solidcraft_engine::view::scene_with_palette(
                 &app.session,
                 &app.cam,
                 crate::viewport::section_plane(app),
                 solidcraft_engine::view::world_curve_parts,
-                &crate::viewport::scene_palette(app.ui.dark),
+                &crate::viewport::scene_palette(app.ui.dark, app.preferences.color_vision),
             );
             let Some(png) = render_png(&scene, &app.cam, w, h) else { return err("render failed") };
             match s("path") {
diff --git a/crates/ui-egui/src/dialogs_assembly.rs b/crates/ui-egui/src/dialogs_assembly.rs
index 3be668a5..76eab174 100644
--- a/crates/ui-egui/src/dialogs_assembly.rs
+++ b/crates/ui-egui/src/dialogs_assembly.rs
@@ -866,7 +866,9 @@ pub fn overlay(app: &SolveApp, painter: &egui::Painter, proj: &Proj, d: &mut Dia
                     continue;
                 }
                 let k = 0.55 + 0.45 * facing;
-                let fill = Color32::from_rgba_unmultiplied((235.0 * k) as u8, (45.0 * k) as u8, (40.0 * k) as u8, 210);
+                let shade = |c: u8| (f64::from(c) * k) as u8;
+                let ic = t.interference;
+                let fill = Color32::from_rgba_unmultiplied(shade(ic.r()), shade(ic.g()), shade(ic.b()), 210);
                 let sp: Vec<Pos2> = ps.iter().filter_map(|p| proj.to_screen(*p)).collect();
                 if sp.len() == 3 {
                     let base = em.vertices.len() as u32;
diff --git a/crates/ui-egui/src/dialogs_sheet.rs b/crates/ui-egui/src/dialogs_sheet.rs
index 144113bd..86f8e04d 100644
--- a/crates/ui-egui/src/dialogs_sheet.rs
+++ b/crates/ui-egui/src/dialogs_sheet.rs
@@ -799,13 +799,11 @@ pub fn arrow(app: &SolveApp, d: &Dialog) -> Option<Vec3> {
     Some(if flip { -n } else { n })
 }
 
-/// Bend line colours: up and down (legible on either theme).
+/// Bend line colours: up and down (theme tokens, legible on either theme and in every colour
+/// vision mode).
 fn bend_colors() -> (Color32, Color32) {
-    if crate::theme::is_dark() {
-        (Color32::from_rgb(110, 200, 120), Color32::from_rgb(240, 150, 80))
-    } else {
-        (Color32::from_rgb(30, 140, 50), Color32::from_rgb(200, 90, 20))
-    }
+    let t = crate::theme::Tokens::get();
+    (t.bend_up, t.bend_down)
 }
 
 /// The flat pattern view: the outline, cut-outs and bend lines (up and down in their colours)
diff --git a/crates/ui-egui/src/gizmo.rs b/crates/ui-egui/src/gizmo.rs
index 3ec9c6c2..47691692 100644
--- a/crates/ui-egui/src/gizmo.rs
+++ b/crates/ui-egui/src/gizmo.rs
@@ -114,14 +114,6 @@ fn ring_basis(i: usize) -> (Vec3, Vec3) {
     }
 }
 
-fn axis_color(i: usize) -> Color32 {
-    match i {
-        0 => Color32::from_rgb(225, 70, 60),
-        1 => Color32::from_rgb(80, 190, 80),
-        _ => Color32::from_rgb(70, 130, 240),
-    }
-}
-
 /// Distance from `p` to the screen segment a–b.
 fn seg_dist(p: Pos2, a: Pos2, b: Pos2) -> f32 {
     let ab = b - a;
@@ -263,7 +255,7 @@ pub fn show(ui: &mut egui::Ui, painter: &egui::Painter, proj: &Proj, id: egui::I
     let hovered = if state.is_none() { pointer.filter(|_| ui.rect_contains_pointer(proj.rect)).and_then(|p| hit(&sh, p)) } else { None };
     let active = state.map(|s| s.handle).or(hovered);
     let hot = |h: Handle| active == Some(h);
-    let col = |h: Handle, i: usize| if hot(h) { tk.accent } else { axis_color(i) };
+    let col = |h: Handle, i: usize| if hot(h) { tk.accent } else { tk.gizmo[i.min(2)] };
     for (i, pts) in &sh.rings {
         painter.add(Shape::line(pts.clone(), Stroke::new(if hot(Handle::Ring(*i)) { 3.0 } else { 1.8 }, col(Handle::Ring(*i), *i))));
     }
diff --git a/crates/ui-egui/src/gpu.rs b/crates/ui-egui/src/gpu.rs
index 85ed6736..1c3c74ef 100644
--- a/crates/ui-egui/src/gpu.rs
+++ b/crates/ui-egui/src/gpu.rs
@@ -13,7 +13,9 @@ use egui_wgpu::wgpu::util::DeviceExt;
 pub const TRI_SIZE: usize = 28;
 /// Line instance: a, b (3 × f32 each), colour (4 × u8), width in pixels (f32).
 pub const LINE_SIZE: usize = 32;
-const UNIFORM_SIZE: u64 = 208;
+/// The shader's `U`: the view-projection matrix, 9 `vec4`s, the 8 analysis colours and their
+/// flags (`uniform_bytes`).
+const UNIFORM_SIZE: u64 = 352;
 
 /// A body drawn from its display plan, evaluated on the GPU: the plan, and a colour per face
 /// (the plan's face numbering; faces past the end take the last colour).
@@ -199,6 +201,8 @@ pub struct ViewportCallback {
     /// Surface analysis: (mode: 0 none, 1 zebra, 2 draft, 3 curvature, 4 environment,
     /// 5 accessibility; parameter; scale; size) and the pull / access direction.
     pub analysis: [f32; 8],
+    /// The analysis colours and the stripe flag ([`analysis_colors`]).
+    pub analysis_colors: [f32; 36],
     /// Accessibility: the depth map seen from the access direction.
     pub access: Option<AccessMap>,
     /// Draw silhouette outlines around the model (visual styles with edges).
@@ -1010,11 +1014,7 @@ impl egui_wgpu::CallbackTrait for ViewportCallback {
     }
 }
 
-/// Render `scene` offscreen on a device of its own, through the viewport's real resources and
-/// frame callback (`prepare`, then `paint`), and read the pixels back: straight RGBA, `size` ×
-/// `size`. `None` without a GPU adapter. With `tess` (the tessellation shader), planned bodies
-/// are evaluated on the GPU where the device builds that pipeline, as [`install`] sets it up.
-/// `highlight` is drawn as the viewport's highlight scene (hover and selection).
+/// A device of its own for an offscreen render or check (`None` without a GPU adapter).
 #[cfg(all(test, not(target_arch = "wasm32")))]
 fn offscreen_device() -> Option<(wgpu::Adapter, wgpu::Device, wgpu::Queue)> {
     let instance = wgpu::Instance::new(wgpu::InstanceDescriptor::new_without_display_handle_from_env());
@@ -1035,7 +1035,15 @@ pub(crate) fn offscreen_tessellates(shader: &str) -> Option<bool> {
     Some(tessellation(&adapter, &device, &queue, shader).is_some())
 }
 
+/// Render `scene` offscreen on a device of its own, through the viewport's real resources and
+/// frame callback (`prepare`, then `paint`), and read the pixels back: straight RGBA, `size` ×
+/// `size`. `None` without a GPU adapter. With `tess` (the tessellation shader), planned bodies
+/// are evaluated on the GPU where the device builds that pipeline, as [`install`] sets it up.
+/// `highlight` is drawn as the viewport's highlight scene (hover and selection). `analysis` is the
+/// surface analysis uniform (`viewport::analysis_uniform`; zeros for none) and `colors` its
+/// colours (`analysis_colors`).
 #[cfg(all(test, not(target_arch = "wasm32")))]
+#[allow(clippy::too_many_arguments)]
 pub(crate) fn render_offscreen(
     scene: GpuScene,
     highlight: Option<GpuScene>,
@@ -1044,6 +1052,8 @@ pub(crate) fn render_offscreen(
     eye: [f32; 4],
     size: u32,
     tess: Option<&str>,
+    analysis: [f32; 8],
+    colors: [f32; 36],
 ) -> Option<Vec<u8>> {
     let (adapter, device, queue) = offscreen_device()?;
     let (format, depth) = (wgpu::TextureFormat::Rgba8Unorm, wgpu::TextureFormat::Depth24PlusStencil8);
@@ -1067,7 +1077,8 @@ pub(crate) fn render_offscreen(
         clip: [0.0; 4],
         cap: [0.0; 4],
         images: Vec::new(),
-        analysis: [0.0; 8],
+        analysis,
+        analysis_colors: colors,
         access: None,
         outline: false,
         eye,
@@ -1152,9 +1163,23 @@ pub fn uniform_bytes(cb: &ViewportCallback, w: f32, h: f32, linear: bool) -> Vec
         None => v.extend([0.0; 8]),
     }
     v.extend(cb.eye);
+    v.extend(cb.analysis_colors);
     v.iter().flat_map(|x| x.to_le_bytes()).collect()
 }
 
+/// The shader's analysis colours (`ana_c`: draft positive, between, negative; reachable,
+/// blocked; curvature flat, middle, tight; alpha 1) and flags (`ana_f.x`: 1 to stripe the bad
+/// faces).
+pub fn analysis_colors(c: &crate::theme::AnalysisColors) -> [f32; 36] {
+    let mut v = [0.0; 36];
+    let colors = c.draft.iter().chain(&c.access).chain(&c.curvature).flat_map(|rgb| [rgb[0], rgb[1], rgb[2], 1.0]);
+    for (slot, x) in v.iter_mut().zip(colors) {
+        *slot = x;
+    }
+    v[32] = if c.hatch { 1.0 } else { 0.0 };
+    v
+}
+
 #[cfg(test)]
 mod tests {
     use egui_wgpu::wgpu::naga;
diff --git a/crates/ui-egui/src/icons.rs b/crates/ui-egui/src/icons.rs
index ded9cf4c..2a5bab03 100644
--- a/crates/ui-egui/src/icons.rs
+++ b/crates/ui-egui/src/icons.rs
@@ -2,6 +2,8 @@
 #[path = "../../../assets/icons/ui/source/icons.rs"]
 mod source;
 pub use source::paint;
+#[cfg(test)]
+pub(crate) use source::paint_with;
 #[path = "../../../assets/icons/ui/source/glyphs.rs"]
 pub(crate) mod glyphs;
 #[path = "../../../assets/icons/ui/source/markers.rs"]
diff --git a/crates/ui-egui/src/lib.rs b/crates/ui-egui/src/lib.rs
index 5b18f1ab..7421b0ae 100644
--- a/crates/ui-egui/src/lib.rs
+++ b/crates/ui-egui/src/lib.rs
@@ -12,6 +12,10 @@ pub mod access;
 pub mod agent_cursor;
 pub mod browser;
 pub mod canvas;
+#[cfg(test)]
+mod colour_tokens_tests;
+#[cfg(test)]
+mod colour_vision_tests;
 pub mod context_menu;
 pub mod control;
 pub mod crash_ui;
@@ -1022,8 +1026,9 @@ impl SolveApp {
         file_load::tick(self, ctx);
         self.esc_handled = false;
         prefs::apply(self, ctx);
-        if !self.styled || theme::is_dark() != self.ui.dark {
+        if !self.styled || theme::is_dark() != self.ui.dark || theme::vision() != self.preferences.color_vision {
             theme::set_dark(self.ui.dark);
+            theme::set_vision(self.preferences.color_vision);
             theme::apply(ctx);
             self.styled = true;
         }
diff --git a/crates/ui-egui/src/prefs.rs b/crates/ui-egui/src/prefs.rs
index b8ab3713..738b76f4 100644
--- a/crates/ui-egui/src/prefs.rs
+++ b/crates/ui-egui/src/prefs.rs
@@ -3,10 +3,10 @@
 //! designs, autosave, display precision, timeline layout, the agent cursor), Navigation (mouse presets, zoom
 //! direction, zoom to the cursor, orbit centre, Look At animation), Keyboard Shortcuts (search,
 //! rebind, conflicts; `keymap`), Design (default modelling orientation, Y up or Z up), Graphics
-//! (visual style, grid, shadow, perspective, anti-aliasing), Sketch and Selection. Changes apply
-//! at once; Cancel puts back what was there when the dialog opened, OK keeps them, Apply keeps
-//! them and stays open, and Restore Defaults resets the page shown. Everything is kept between
-//! runs, except anti-aliasing, which needs a restart.
+//! (visual style, grid, shadow, perspective, anti-aliasing, colour vision), Sketch and Selection.
+//! Changes apply at once; Cancel puts back what was there when the dialog opened, OK keeps them,
+//! Apply keeps them and stays open, and Restore Defaults resets the page shown. Everything is
+//! kept between runs, except anti-aliasing, which needs a restart.
 
 use egui::{Modifiers, Pos2, RichText};
 use serde::{Deserialize, Serialize};
@@ -246,6 +246,8 @@ pub struct Prefs {
     pub offer_stand_up: bool,
     /// What a middle-button double-click in the view does: `home`, `fit` or `off`.
     pub middle_double_click: String,
+    /// Colour vision mode (#778): `off`, `protan`, `deutan` or `tritan`.
+    pub color_vision: crate::theme::ColorVision,
     /// Check for updates at start and once a day (docs/updates.md).
     pub check_updates: bool,
     /// When the last update check ran, and the versions skipped or put off (`update::Memo`).
@@ -308,6 +310,7 @@ impl Default for Prefs {
             up_axis: "z".into(),
             offer_stand_up: true,
             middle_double_click: "home".into(),
+            color_vision: crate::theme::ColorVision::Off,
             check_updates: true,
             update: crate::update::Memo::default(),
         }
@@ -431,6 +434,7 @@ fn defaults(app: &mut SolveApp, page: usize) {
         PAGE_GRAPHICS => {
             let msaa = p.msaa != d.msaa;
             p.msaa = d.msaa;
+            p.color_vision = d.color_vision;
             app.ui.visual_style = 0;
             app.ui.show_grid = true;
             app.ui.ground_shadow = true;
@@ -1055,6 +1059,28 @@ fn page(app: &mut SolveApp, ui: &mut egui::Ui, t: &Tokens) {
                 _ => "CPU (software)".to_string(),
             });
             ui.end_row();
+            // Colour vision (#778): its own section at the end of the page.
+            ui.label("");
+            ui.end_row();
+            ui.label(RichText::new(app.tr("ui.colour_vision")).strong());
+            ui.label("");
+            ui.end_row();
+            ui.label(app.tr("ui.colour_vision_mode"));
+            let mode = app.preferences.color_vision;
+            egui::ComboBox::from_id_salt("pref_color_vision").selected_text(app.tr(mode.label_id())).show_ui(ui, |ui| {
+                for m in crate::theme::ColorVision::ALL {
+                    ui.selectable_value(&mut app.preferences.color_vision, m, crate::i18n::tr(m.label_id())).on_hover_text(crate::i18n::tr(m.help_id()));
+                }
+            });
+            if app.preferences.color_vision != mode {
+                // At once, like the theme: the next frame draws in the new colours.
+                ui.ctx().request_repaint();
+            }
+            ui.end_row();
+            ui.label(app.tr("ui.colour_vision_sample"));
+            colour_vision_sample(ui, t);
+            ui.end_row();
+            note(ui, app.tr("ui.colour_vision_note"));
         }
         5 => {
             ui.label(crate::i18n::tr_label("Project face edges into new sketches"));
@@ -1072,6 +1098,76 @@ fn page(app: &mut SolveApp, ui: &mut egui::Ui, t: &Tokens) {
     });
 }
 
+/// The names under the Colour vision sample (message ids).
+pub(crate) const COLOUR_VISION_SAMPLE: [&str; 6] =
+    ["ui.colour_vision_fixed", "ui.colour_vision_projected", "ui.axes", "Bends", "ui.draft", "ui.colour_vision_failed"];
+
+/// The Colour vision sample (#778): fixed and projected sketch lines, the X and Y axes, bends up
+/// and down, Draft Analysis and a failed feature, each drawn as it is where it appears, in the
+/// colours on now. One fixed-size area, so the grid row is as tall as what it draws.
+fn colour_vision_sample(ui: &mut egui::Ui, t: &Tokens) {
+    const W: f32 = 72.0;
+    const LINE: f32 = 4.0;
+    let (area, _) = ui.allocate_exact_size(egui::vec2(W * COLOUR_VISION_SAMPLE.len() as f32, 50.0), egui::Sense::hover());
+    let p = ui.painter_at(area);
+    let line = |c| egui::Stroke::new(LINE, c);
+    for (i, name) in COLOUR_VISION_SAMPLE.iter().enumerate() {
+        let cell = egui::Rect::from_min_size(area.min + egui::vec2(W * i as f32, 0.0), egui::vec2(W - 8.0, 32.0));
+        let (a, b) = (cell.left_center() + egui::vec2(8.0, 0.0), cell.right_center() - egui::vec2(8.0, 0.0));
+        match i {
+            0 | 1 => {
+                p.rect_filled(cell, 3.0, t.viewport_top);
+                p.line_segment([a, b], line(if i == 0 { t.sketch_locked } else { t.sketch_projected }));
+            }
+            2 => {
+                // X along and Y up from one corner, as the view triad draws them.
+                p.rect_filled(cell, 3.0, t.viewport_top);
+                let o = cell.left_bottom() + egui::vec2(12.0, -7.0);
+                p.line_segment([o, egui::pos2(cell.right() - 10.0, o.y)], line(t.triad[0]));
+                p.line_segment([o, egui::pos2(o.x, cell.top() + 6.0)], line(t.triad[1]));
+            }
+            3 => {
+                // Dashed, as the flat pattern draws them.
+                p.rect_filled(cell, 3.0, t.viewport_top);
+                for (dy, c) in [(-7.0, t.bend_up), (7.0, t.bend_down)] {
+                    p.extend(egui::Shape::dashed_line(&[a + egui::vec2(0.0, dy), b + egui::vec2(0.0, dy)], line(c), 8.0, 5.0));
+                }
+            }
+            4 => {
+                // The three bands of Draft Analysis; in a mode the negative one is striped.
+                let w = cell.width() / 3.0;
+                for (k, c) in t.analysis.draft.iter().enumerate() {
+                    let band = egui::Rect::from_min_size(cell.min + egui::vec2(w * k as f32, 0.0), egui::vec2(w, cell.height()));
+                    p.rect_filled(band, 0.0, crate::theme::srgb(*c));
+                    if k == 2 && t.analysis.hatch {
+                        let stripes = p.with_clip_rect(band);
+                        let dark = crate::theme::srgb(c.map(|x| x * 0.6));
+                        let mut x = band.left() - band.height();
+                        while x < band.right() {
+                            stripes.line_segment(
+                                [egui::pos2(x, band.bottom()), egui::pos2(x + band.height(), band.top())],
+                                egui::Stroke::new(2.0, dark),
+                            );
+                            x += 9.0;
+                        }
+                    }
+                }
+            }
+            _ => {
+                // A failed feature on the timeline.
+                p.rect(cell.shrink2(egui::vec2(10.0, 3.0)), 3.0, t.timeline_item_error, egui::Stroke::new(1.0, t.error), egui::StrokeKind::Inside);
+            }
+        }
+        p.text(
+            cell.center_bottom() + egui::vec2(0.0, 3.0),
+            egui::Align2::CENTER_TOP,
+            crate::i18n::tr(name),
+            egui::FontId::proportional(11.0),
+            t.text_dim,
+        );
+    }
+}
+
 /// The control channel's `ui.prefs`: `open` (a page name) opens the dialog there, `button`
 /// presses OK, Cancel, Apply or Restore Defaults, `stand_up: true` answers the stand-up offer;
 /// any other keys set preferences. Returns them all, the open page and the offer.
@@ -1142,6 +1238,12 @@ pub fn set(app: &mut SolveApp, p: &serde_json::Value) -> Result<serde_json::Valu
             o.insert(k.clone(), v.clone());
         }
     }
+    // Saved preferences read an unknown mode as Off; asked for here, it is an error.
+    if let Some(v) = p.get("color_vision")
+        && v.as_str().and_then(crate::theme::ColorVision::from_id).is_none()
+    {
+        return Err("`color_vision` must be off, protan, deutan or tritan".into());
+    }
     let new: Prefs = serde_json::from_value(cur).map_err(|e| e.to_string())?;
     if !UNITS.contains(&new.default_units.as_str()) {
         return Err(format!("units must be one of {}", UNITS.join(", ")));
diff --git a/crates/ui-egui/src/theme.rs b/crates/ui-egui/src/theme.rs
index 7195df15..9cb26a78 100644
--- a/crates/ui-egui/src/theme.rs
+++ b/crates/ui-egui/src/theme.rs
@@ -1,21 +1,163 @@
 //! Colours and widget style: a dark theme (the default, a blue-grey in the spirit of desktop CAD
-//! tools, viewport #2e3440) and a light one. Every colour the UI uses comes from [`Tokens`].
+//! tools, viewport #2e3440) and a light one, each with colour vision modes. Every colour the UI
+//! uses comes from [`Tokens`].
 
+use std::cell::Cell;
 use std::sync::atomic::{AtomicBool, Ordering};
 
 #[path = "../../../assets/styles/ui/palettes.rs"]
 mod palettes;
 
 use egui::{Color32, Stroke};
+use serde::{Deserialize, Serialize};
 
 static DARK: AtomicBool = AtomicBool::new(true);
 
+thread_local! {
+    /// The colour vision mode, per thread, where the dark theme is one global (`DARK`). Each app
+    /// sets it from its own preferences at the start of every frame (`SolveApp::logic`), on the
+    /// thread that draws it. Tests run many apps side by side on their own threads in one process:
+    /// with one global, a test in a mode changed the colours under another one
+    /// (`hover_stays_off_during_spin_and_animated_views` failed that way). No worker thread reads
+    /// it: the preview thread is handed its colours (`preview::Colors`) and thumbnails are drawn by
+    /// the engine in the model's colours, so a new thread starts Off and stays Off.
+    static VISION: Cell<ColorVision> = const { Cell::new(ColorVision::Off) };
+}
+
 /// Is the dark theme on?
 pub fn is_dark() -> bool {
     DARK.load(Ordering::Relaxed)
 }
 
-#[derive(Clone, Copy, Debug)]
+/// Colour vision modes (#778): a second set of values for the colours that carry a meaning, for
+/// a weak or missing red (protan), green (deutan) or blue (tritan) sense. Not a filter: Off gives
+/// back the theme's colours unchanged. Protan and Deutan share one red-green table, measured
+/// clear for both (`colour_vision_tests`).
+#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, Hash, Serialize)]
+#[serde(rename_all = "snake_case")]
+pub enum ColorVision {
+    #[default]
+    Off,
+    Protan,
+    Deutan,
+    Tritan,
+}
+
+impl ColorVision {
+    pub const ALL: [ColorVision; 4] = [ColorVision::Off, ColorVision::Protan, ColorVision::Deutan, ColorVision::Tritan];
+
+    /// The saved value (`ui.prefs` `color_vision`).
+    pub fn id(self) -> &'static str {
+        match self {
+            ColorVision::Off => "off",
+            ColorVision::Protan => "protan",
+            ColorVision::Deutan => "deutan",
+            ColorVision::Tritan => "tritan",
+        }
+    }
+
+    pub fn from_id(id: &str) -> Option<ColorVision> {
+        ColorVision::ALL.into_iter().find(|m| m.id() == id)
+    }
+
+    /// Its name in the Preferences (a message id).
+    pub fn label_id(self) -> &'static str {
+        match self {
+            ColorVision::Off => "ui.colour_vision_off",
+            ColorVision::Protan => "ui.colour_vision_protan",
+            ColorVision::Deutan => "ui.colour_vision_deutan",
+            ColorVision::Tritan => "ui.colour_vision_tritan",
+        }
+    }
+
+    /// Who it is for, in one line (its tooltip; a message id).
+    pub fn help_id(self) -> &'static str {
+        match self {
+            ColorVision::Off => "ui.colour_vision_off_tip",
+            ColorVision::Protan => "ui.colour_vision_protan_tip",
+            ColorVision::Deutan => "ui.colour_vision_deutan_tip",
+            ColorVision::Tritan => "ui.colour_vision_tritan_tip",
+        }
+    }
+}
+
+/// From saved preferences: a value this version doesn't know (a later version's mode, a hand
+/// edit) is Off rather than an error, which would lose every other saved preference with it.
+/// `ui.prefs` refuses such a value before it gets here (`prefs::set`).
+impl<'de> Deserialize<'de> for ColorVision {
+    fn deserialize<D: serde::Deserializer<'de>>(d: D) -> Result<Self, D::Error> {
+        let v = serde_json::Value::deserialize(d)?;
+        Ok(v.as_str().and_then(ColorVision::from_id).unwrap_or_default())
+    }
+}
+
+/// The colour vision mode on now (on this thread).
+pub fn vision() -> ColorVision {
+    VISION.with(Cell::get)
+}
+
+/// Switch the colour vision mode (the visuals follow on the next [`apply`]).
+pub fn set_vision(mode: ColorVision) {
+    VISION.with(|v| v.set(mode));
+}
+
+/// An sRGB colour given as 0..1 (the analysis colours), for drawing in the UI.
+pub fn srgb(c: [f32; 3]) -> Color32 {
+    let byte = |x: f32| (x.clamp(0.0, 1.0) * 255.0).round() as u8;
+    Color32::from_rgb(byte(c[0]), byte(c[1]), byte(c[2]))
+}
+
+/// Surface analysis colours, straight sRGB 0..1 as the shader takes them (exact, so they read
+/// the same as when they were literals in the WGSL).
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct AnalysisColors {
+    /// Draft Analysis: at least the draft angle, between, at most minus the angle.
+    pub draft: [[f32; 3]; 3],
+    /// Accessibility Analysis: reachable, blocked.
+    pub access: [[f32; 3]; 2],
+    /// Curvature Map: flat, the middle of the scale, at or below the analysis radius.
+    pub curvature: [[f32; 3]; 3],
+    /// Stripe the negative draft and blocked faces too, so colour is not the only cue.
+    pub hatch: bool,
+}
+
+/// The colours icons draw of their own (`icons::paint` takes ink, fill and accent from its
+/// caller). Every icon colour is a token so a colour vision mode can reach it.
+#[derive(Clone, Copy, Debug, PartialEq)]
+pub struct IconColors {
+    /// Surface sheets: a sheet, a second sheet beside it, a lighter sheet, iso lines and teeth.
+    pub sheet: Color32,
+    pub sheet_2: Color32,
+    pub sheet_light: Color32,
+    pub sheet_line: Color32,
+    /// Highlights (and the white ink of markers and the agent pointer), and the sphere's glint.
+    pub highlight: Color32,
+    pub glint: Color32,
+    pub folder: Color32,
+    pub plane: Color32,
+    pub fold: Color32,
+    /// Zebra stripes, and the environment map's sky and floor.
+    pub stripe: Color32,
+    pub sky: Color32,
+    pub floor: Color32,
+    /// Appearance: red, blue and yellow paint dabs.
+    pub paint: [Color32; 3],
+    /// Origin: X, Y and Z arrows.
+    pub axes: [Color32; 3],
+    /// Accessibility: reachable, blocked. Draft: positive, between. Curvature: flat, middle,
+    /// tight.
+    pub access: [Color32; 2],
+    pub draft: [Color32; 2],
+    pub curvature: [Color32; 3],
+    pub interference: Color32,
+    pub warning: Color32,
+    /// The pointer an AI agent moves.
+    pub agent: Color32,
+    /// The dark halo under viewport markers (snap points).
+    pub marker_halo: Color32,
+}
+
+#[derive(Clone, Copy, Debug, PartialEq)]
 pub struct Tokens {
     pub app_bar: Color32,
     pub toolbar: Color32,
@@ -135,12 +277,49 @@ pub struct Tokens {
     // ---- box selection ----
     pub box_window: Color32,
     pub box_crossing: Color32,
+    // ---- colours that came from the engine or were drawn in place ----
+    /// Sketch curves the engine tags (`view::colors`): projected, lost link, construction,
+    /// centerline.
+    pub sketch_projected: Color32,
+    pub sketch_lost: Color32,
+    pub sketch_construction: Color32,
+    pub sketch_centerline: Color32,
+    /// The view triad's X, Y and Z (and the CPU scene's origin axes).
+    pub triad: [Color32; 3],
+    /// The move gizmo's X, Y and Z.
+    pub gizmo: [Color32; 3],
+    /// Sheet metal flat pattern: bend up, bend down.
+    pub bend_up: Color32,
+    pub bend_down: Color32,
+    /// Interference: the clash fill, before its shading.
+    pub interference: Color32,
+    pub analysis: AnalysisColors,
+    pub icons: IconColors,
+    /// The application bar's buttons: ink, fill and accent of their icons.
+    pub app_bar_icon: [Color32; 3],
+    /// The SolidCraft mark on the application bar: light, mid and dark faces, and its edge.
+    pub logo: [Color32; 4],
 }
 
 impl Tokens {
-    /// The tokens of the current theme.
+    /// The tokens of the current theme and colour vision mode.
     pub fn get() -> Tokens {
-        if is_dark() { Tokens::dark() } else { Tokens::light() }
+        Tokens::themed(is_dark(), vision())
+    }
+
+    /// The tokens of a theme and colour vision mode.
+    pub fn themed(dark: bool, mode: ColorVision) -> Tokens {
+        (if dark { Tokens::dark() } else { Tokens::light() }).with_vision(dark, mode)
+    }
+
+    /// These tokens with a colour vision mode's values on top (the tables in `palettes.rs`); Off
+    /// gives them back unchanged.
+    pub fn with_vision(self, dark: bool, mode: ColorVision) -> Tokens {
+        match mode {
+            ColorVision::Off => self,
+            ColorVision::Protan | ColorVision::Deutan => self.red_green(dark),
+            ColorVision::Tritan => self.blue_yellow(dark),
+        }
     }
 
     /// Fade idle cube colours into the viewport while retaining opaque facets.
@@ -170,7 +349,7 @@ pub fn set_dark(dark: bool) {
 }
 
 fn visuals(dark: bool) -> egui::Visuals {
-    let t = if dark { Tokens::dark() } else { Tokens::light() };
+    let t = Tokens::themed(dark, vision());
     let mut v = if dark { egui::Visuals::dark() } else { egui::Visuals::light() };
     v.panel_fill = t.panel;
     v.window_fill = t.panel;
diff --git a/crates/ui-egui/src/toolbar.rs b/crates/ui-egui/src/toolbar.rs
index 903b222b..8c5eb952 100644
--- a/crates/ui-egui/src/toolbar.rs
+++ b/crates/ui-egui/src/toolbar.rs
@@ -187,14 +187,7 @@ pub fn app_bar(app: &mut SolveApp, ui: &mut egui::Ui) {
                 ui.painter().rect_filled(br, 4.0, Color32::from_white_alpha(30));
             }
             let dim = |c: Color32| if enabled { c } else { c.gamma_multiply(0.35) };
-            icons::paint(
-                ui.painter(),
-                br.shrink(5.0),
-                icon,
-                dim(Color32::from_rgb(225, 230, 238)),
-                dim(Color32::from_rgb(120, 140, 170)),
-                dim(Color32::from_rgb(120, 190, 255)),
-            );
+            icons::paint(ui.painter(), br.shrink(5.0), icon, dim(t.app_bar_icon[0]), dim(t.app_bar_icon[1]), dim(t.app_bar_icon[2]));
             let clicked = resp.on_hover_text(tip).clicked();
             enabled && clicked
         };
diff --git a/crates/ui-egui/src/viewport.rs b/crates/ui-egui/src/viewport.rs
index 77057d62..86e833ca 100644
--- a/crates/ui-egui/src/viewport.rs
+++ b/crates/ui-egui/src/viewport.rs
@@ -279,6 +279,7 @@ fn scene_key(app: &SolveApp) -> u64 {
     app.preview.replaced.hash(&mut h);
     app.tree.redefine.hash(&mut h);
     crate::theme::is_dark().hash(&mut h);
+    crate::theme::vision().hash(&mut h);
     app.session.active_sketch.hash(&mut h);
     h.finish()
 }
@@ -296,7 +297,7 @@ pub(crate) fn display_scene_keys(app: &SolveApp, proj: &Proj) -> (u64, u64) {
     (scene_key(app), sketch_scene_key(app, proj))
 }
 
-/// A sketch curve colour from the engine, in the current theme.
+/// A sketch curve colour from the engine, in the current theme and colour vision mode.
 fn sketch_color(t: &Tokens, c: Rgb) -> [u8; 4] {
     if c == colors::SKETCH {
         c4(t.sketch)
@@ -304,6 +305,14 @@ fn sketch_color(t: &Tokens, c: Rgb) -> [u8; 4] {
         c4(t.sketch_fixed)
     } else if c == colors::SKETCH_LOCKED {
         c4(t.sketch_locked)
+    } else if c == colors::SKETCH_PROJECTED {
+        c4(t.sketch_projected)
+    } else if c == colors::SKETCH_LOST {
+        c4(t.sketch_lost)
+    } else if c == colors::SKETCH_CONSTRUCTION {
+        c4(t.sketch_construction)
+    } else if c == colors::SKETCH_CENTERLINE {
+        c4(t.sketch_centerline)
     } else {
         rgba(c)
     }
@@ -1554,6 +1563,7 @@ fn highlight_key(app: &SolveApp) -> u64 {
     app.ui.visual_style.hash(&mut h);
     app.ui.pick_bodies.hash(&mut h);
     crate::theme::is_dark().hash(&mut h);
+    crate::theme::vision().hash(&mut h);
     app.preview.replaced.hash(&mut h);
     app.origin_visible().hash(&mut h);
     app.session.visibility.hidden_origin.hash(&mut h);
@@ -2263,6 +2273,7 @@ pub fn show(app: &mut SolveApp, ui: &mut egui::Ui) {
             size_px: [rect.width() * ppp, rect.height() * ppp],
             images: crate::ref_images::gpu_images(app),
             analysis: analysis_uniform(app),
+            analysis_colors: crate::gpu::analysis_colors(&t.analysis),
             access: crate::access::map(app),
             outline: matches!(app.ui.visual_style, 0 | 3),
             eye: {
@@ -2981,10 +2992,11 @@ fn cpu_render(app: &mut SolveApp, ctx: &egui::Context, painter: &egui::Painter,
     }
     (rect.width() as u32, rect.height() as u32).hash(&mut h);
     app.ui.dark.hash(&mut h);
+    app.preferences.color_vision.hash(&mut h);
     let key = h.finish();
     if app.viewport.cpu.as_ref().is_none_or(|(k, _)| *k != key) {
         let mut budget = solidcraft_engine::render::SamplingBudget::new(131_072, 1_048_576);
-        let palette = scene_palette(app.ui.dark);
+        let palette = scene_palette(app.ui.dark, app.preferences.color_vision);
         let scene = solidcraft_engine::view::scene_with_palette(
             &app.session,
             &proj.cam,
@@ -3005,11 +3017,11 @@ fn cpu_render(app: &mut SolveApp, ctx: &egui::Context, painter: &egui::Painter,
 }
 
 /// The colours of a CPU picture of the model (`ui.render` and the CPU viewport) in the dark or
-/// the light theme, from the tokens the window draws with, so the picture matches the window. The
-/// light theme's are the engine's own colours, so a light render is unchanged. The sketch states
-/// and axes the window draws in the engine's colours stay so.
-pub(crate) fn scene_palette(dark: bool) -> solidcraft_engine::view::Palette {
-    let t = if dark { Tokens::dark() } else { Tokens::light() };
+/// the light theme and a colour vision mode, from the tokens the window draws with, so the picture
+/// matches the window. The light theme's tokens (Off) are the engine's own colours, so a light
+/// render is unchanged.
+pub(crate) fn scene_palette(dark: bool, mode: crate::theme::ColorVision) -> solidcraft_engine::view::Palette {
+    let t = Tokens::themed(dark, mode);
     let rgb = |c: Color32| Rgb(c.r(), c.g(), c.b());
     solidcraft_engine::view::Palette {
         background: (rgb(t.viewport_top), rgb(t.viewport_bottom)),
@@ -3022,8 +3034,12 @@ pub(crate) fn scene_palette(dark: bool) -> solidcraft_engine::view::Palette {
         sketch_fixed: rgb(t.sketch_fixed),
         sketch_done: rgb(t.sketch_fixed),
         sketch_locked: rgb(t.sketch_locked),
+        sketch_projected: rgb(t.sketch_projected),
+        sketch_lost: rgb(t.sketch_lost),
+        sketch_construction: rgb(t.sketch_construction),
+        sketch_centerline: rgb(t.sketch_centerline),
+        axes: t.triad.map(rgb),
         cap: rgb(t.section_cap),
-        ..solidcraft_engine::view::Palette::DEFAULT
     }
 }
 
@@ -3467,7 +3483,21 @@ mod tests {
             let e = proj.cam.eye().to_f32();
             let eye = [e[0], e[1], e[2], if proj.cam.fov > 0.0 { 1.0 } else { 0.0 }];
             let (planned, shader) = (scene.planned.len(), tess.then_some(solidcraft_gpu::SHADER));
-            (planned, scene.tris.len(), crate::gpu::render_offscreen(scene, None, proj.vp.to_f32(), proj.cam.back().to_f32(), eye, SIZE, shader))
+            (
+                planned,
+                scene.tris.len(),
+                crate::gpu::render_offscreen(
+                    scene,
+                    None,
+                    proj.vp.to_f32(),
+                    proj.cam.back().to_f32(),
+                    eye,
+                    SIZE,
+                    shader,
+                    [0.0; 8],
+                    crate::gpu::analysis_colors(&Tokens::get().analysis),
+                ),
+            )
         };
         let (planned, gpu_tris, gpu) = render(true);
         let (none, cpu_tris, cpu) = render(false);
@@ -3516,7 +3546,17 @@ mod tests {
         let proj = projection(&app, rect);
         let e = proj.cam.eye().to_f32();
         let eye = [e[0], e[1], e[2], if proj.cam.fov > 0.0 { 1.0 } else { 0.0 }];
-        let Some(img) = crate::gpu::render_offscreen(scene, None, proj.vp.to_f32(), proj.cam.back().to_f32(), eye, SIZE, Some(REJECTED)) else {
+        let Some(img) = crate::gpu::render_offscreen(
+            scene,
+            None,
+            proj.vp.to_f32(),
+            proj.cam.back().to_f32(),
+            eye,
+            SIZE,
+            Some(REJECTED),
+            [0.0; 8],
+            crate::gpu::analysis_colors(&Tokens::get().analysis),
+        ) else {
             return;
         };
         let n = (SIZE * SIZE) as usize;
@@ -3552,7 +3592,17 @@ mod tests {
             let e = proj.cam.eye().to_f32();
             let eye = [e[0], e[1], e[2], if proj.cam.fov > 0.0 { 1.0 } else { 0.0 }];
             let shader = tess.then_some(solidcraft_gpu::SHADER);
-            crate::gpu::render_offscreen(scene, Some(highlight), proj.vp.to_f32(), proj.cam.back().to_f32(), eye, SIZE, shader)
+            crate::gpu::render_offscreen(
+                scene,
+                Some(highlight),
+                proj.vp.to_f32(),
+                proj.cam.back().to_f32(),
+                eye,
+                SIZE,
+                shader,
+                [0.0; 8],
+                crate::gpu::analysis_colors(&Tokens::get().analysis),
+            )
         };
         let lit = |plain: &[u8], hovered: &[u8]| -> Vec<bool> { plain.chunks(4).zip(hovered.chunks(4)).map(|(a, b)| a != b).collect() };
         let (Some(gpu_plain), Some(cpu_plain)) = (render(true, None), render(false, None)) else {
@@ -3628,24 +3678,27 @@ mod tests {
         crate::sketch_palette::set_mode(&mut h.app, 0);
     }
 
-    /// The CPU pictures (`ui.render`, the CPU viewport) are drawn in the window's theme (#974).
-    /// The light theme's tokens are the engine's own colours, so a light picture is unchanged; in
-    /// the dark theme each part takes the token the window draws it with. Sketch states follow
-    /// what the window does with them (`sketch_color`), so the two can't drift apart.
+    /// The CPU pictures (`ui.render`, the CPU viewport) are drawn in the window's theme (#974)
+    /// and colour vision mode (#778). The light theme's tokens are the engine's own colours, so a
+    /// light picture in Off is unchanged; otherwise each part takes the token the window draws it
+    /// with. Sketch states follow what the window does with them (`sketch_color`) and the axes the
+    /// mode's triad, so the two can't drift apart.
     #[test]
     fn cpu_pictures_are_drawn_in_the_windows_theme() {
+        use crate::theme::ColorVision;
         use solidcraft_engine::view::Palette;
-        assert_eq!(scene_palette(false), Palette::DEFAULT, "the light theme is the engine's colours");
+        assert_eq!(scene_palette(false, ColorVision::Off), Palette::DEFAULT, "the light theme is the engine's colours");
         let rgb = |c: Color32| Rgb(c.r(), c.g(), c.b());
-        let (p, t) = (scene_palette(true), Tokens::dark());
+        let (p, t) = (scene_palette(true, ColorVision::Off), Tokens::dark());
         assert_eq!(p.background, (rgb(t.viewport_top), rgb(t.viewport_bottom)));
         assert_eq!(
             [p.grid, p.grid_major, p.edge, p.body, p.body_selected, p.cap],
             [t.grid, t.grid_major, t.body_edge, t.body, t.body_selected, t.section_cap].map(rgb)
         );
         assert_ne!(p.background, Palette::DEFAULT.background);
-        for dark in [false, true] {
-            let (p, t) = (scene_palette(dark), if dark { Tokens::dark() } else { Tokens::light() });
+        for (dark, mode) in [false, true].into_iter().flat_map(|d| ColorVision::ALL.map(|m| (d, m))) {
+            let (p, t) = (scene_palette(dark, mode), Tokens::themed(dark, mode));
+            assert_eq!(p.axes, t.triad.map(rgb), "dark {dark}, {mode:?}: the axes");
             for (tag, cpu) in [
                 (colors::SKETCH, p.sketch),
                 (colors::SKETCH_FIXED, p.sketch_fixed),
@@ -3657,12 +3710,13 @@ mod tests {
                 (colors::SKETCH_CENTERLINE, p.sketch_centerline),
             ] {
                 let [r, g, b, _] = sketch_color(&t, tag);
-                assert_eq!(cpu, Rgb(r, g, b), "dark {dark}: the window draws {tag:?} in another colour");
+                assert_eq!(cpu, Rgb(r, g, b), "dark {dark}, {mode:?}: the window draws {tag:?} in another colour");
             }
         }
     }
 
-    /// The CPU viewport follows a theme change at once: the theme is part of its picture's key.
+    /// The CPU viewport follows a theme or colour vision mode change at once: both are part of its
+    /// picture's key.
     #[test]
     fn cpu_viewport_redraws_in_the_new_theme() {
         let mut h = crate::scenario::Harness::new();
@@ -3696,6 +3750,10 @@ mod tests {
             let near = [px.r(), px.g(), px.b()].iter().zip([want.r(), want.g(), want.b()]).all(|(a, b)| a.abs_diff(b) <= 2);
             assert!(near, "dark {dark}: top row {px:?}, the window's background {want:?}");
         }
+        // And a colour vision mode change, on its own.
+        h.app.preferences.color_vision = crate::theme::ColorVision::Deutan;
+        assert!(top_row(&mut h).is_some(), "a new mode kept the old picture");
+        assert!(top_row(&mut h).is_none(), "no change, no new picture");
     }
 
     #[test]
@@ -5012,6 +5070,171 @@ mod tests {
         app.session.visibility.hidden_origin.push(name);
         assert!(construction_axis_segments(&app).is_empty());
     }
+
+    /// Draft Analysis on the GPU takes its colours from the tokens: the sample design through the
+    /// viewport's real pipeline, offscreen (skipped without a GPU). In Off the faces that pass are
+    /// green; in Protan they are the red-green table's blue, and the negative faces are striped.
+    #[cfg(not(target_arch = "wasm32"))]
+    #[test]
+    fn draft_analysis_on_the_gpu_draws_the_modes_colours_and_stripes() {
+        use crate::theme::ColorVision;
+        let mut s = solidcraft_engine::Session::default();
+        s.run_script(&solidcraft_engine::sample::script()).unwrap();
+        let mut app = SolveApp::new(s, crate::Services::default());
+        app.viewport.no_pixels = true;
+        app.fit_view();
+        app.run("inspect.draft", json!({"pull": [-1, -1, 0]})).unwrap();
+        app.viewport.gpu = Some(GpuTarget { format: egui_wgpu::wgpu::TextureFormat::Rgba8Unorm, depth: None, samples: 1, tess: false });
+        const SIZE: u32 = 256;
+        let proj = projection(&app, Rect::from_min_size(Pos2::ZERO, vec2(SIZE as f32, SIZE as f32)));
+        let e = proj.cam.eye().to_f32();
+        let eye = [e[0], e[1], e[2], if proj.cam.fov > 0.0 { 1.0 } else { 0.0 }];
+        let render = |c: &crate::theme::AnalysisColors| {
+            crate::gpu::render_offscreen(
+                build_scene(&app),
+                None,
+                proj.vp.to_f32(),
+                proj.cam.back().to_f32(),
+                eye,
+                SIZE,
+                None,
+                analysis_uniform(&app),
+                crate::gpu::analysis_colors(c),
+            )
+        };
+        let off = Tokens::themed(false, ColorVision::Off).analysis;
+        let protan = Tokens::themed(false, ColorVision::Protan).analysis;
+        let flat = crate::theme::AnalysisColors { hatch: false, ..protan };
+        let (Some(a), Some(b), Some(c)) = (render(&off), render(&protan), render(&flat)) else {
+            eprintln!("skipping: no GPU adapter");
+            return;
+        };
+        // Pixels of a colour under any light: the same hue, so the same ratios between channels.
+        let like = |img: &[u8], c: [f32; 3]| {
+            img.as_chunks::<4>()
+                .0
+                .iter()
+                .filter(|p| {
+                    let m = c.iter().copied().fold(0.0, f32::max);
+                    let k = f32::from(p[0].max(p[1]).max(p[2])) / 255.0 / m;
+                    k > 0.3 && (0..3).all(|i| (f32::from(p[i]) / 255.0 - c[i] * k).abs() < 0.04)
+                })
+                .count()
+        };
+        let n = (SIZE * SIZE) as usize;
+        assert!(like(&a, off.draft[0]) > n / 50 && like(&a, protan.draft[0]) == 0, "Off: green passing faces");
+        assert!(like(&b, protan.draft[0]) > n / 50 && like(&b, off.draft[0]) == 0, "Protan: blue passing faces");
+        // The stripes: with them on, some negative pixels are darker, and nothing else changes.
+        let negative = |p: &[u8]| like(p, protan.draft[2]) == 1;
+        let changed: Vec<usize> = (0..n).filter(|&i| b[4 * i..4 * i + 3] != c[4 * i..4 * i + 3]).collect();
+        let neg = (0..n).filter(|&i| negative(&c[4 * i..4 * i + 4])).count();
+        assert!(!changed.is_empty() && changed.len() * 2 < neg, "{} striped of {neg} negative pixels", changed.len());
+        assert!(changed.iter().all(|&i| negative(&c[4 * i..4 * i + 4])), "only negative faces are striped");
+        assert!(changed.iter().all(|&i| b[4 * i..4 * i + 3].iter().zip(&c[4 * i..4 * i + 3]).all(|(x, y)| x <= y)), "stripes are darker");
+    }
+
+    /// The CPU viewport draws in the colour vision mode: a fixed sketch line in the light theme
+    /// takes Deutan's value, and Off's is gone.
+    #[test]
+    fn cpu_viewport_draws_in_the_colour_vision_mode() {
+        use crate::theme::ColorVision;
+        let mut h = crate::scenario::Harness::new();
+        h.app.ui.dark = false;
+        h.app.run("sketch.create", json!({"plane": "XY"})).unwrap();
+        let made = h.app.run("sketch.line", json!({"points": [[-30, -20], [30, 20]]})).unwrap();
+        h.app.run("sketch.constraint.fix", json!({"entity": made["created"]["curves"][0]})).unwrap();
+        let rect = Rect::from_min_size(Pos2::ZERO, vec2(320.0, 240.0));
+        let mut cam = solidcraft_engine::view::home_camera(&h.app.session);
+        cam.set_view(solidcraft_engine::render::StandardView::Top);
+        let proj = Proj { cam, vp: cam.view_proj(4.0 / 3.0, 100.0), rect };
+        h.app.viewport.no_pixels = false;
+        let count = |h: &mut crate::scenario::Harness, c: Color32| {
+            h.app.viewport.cpu = None;
+            let mut out = h.ctx.run_ui(egui::RawInput { screen_rect: Some(rect), ..Default::default() }, |ui| {
+                cpu_render(&mut h.app, ui.ctx(), ui.painter(), rect, &proj);
+            });
+            let id = h.app.viewport.cpu.as_ref().map(|(_, tex)| tex.id());
+            let n = id.and_then(|id| out.textures_delta.set.get(&id)).and_then(|d| d.iter().find(|delta| delta.pos.is_none())).map_or(0, |upload| {
+                let egui::ImageData::Color(image) = &upload.image;
+                image.pixels.iter().filter(|p| [p.r(), p.g(), p.b()].iter().zip([c.r(), c.g(), c.b()]).all(|(a, b)| a.abs_diff(b) <= 8)).count()
+            });
+            out.textures_delta.clear();
+            n
+        };
+        let (off, deutan) = (Tokens::light().sketch_locked, Tokens::themed(false, ColorVision::Deutan).sketch_locked);
+        let (a, b) = (count(&mut h, off), count(&mut h, deutan));
+        assert!(a > 20 && b == 0, "Off: {a} fixed-line pixels, {b} in Deutan's colour");
+        h.app.preferences.color_vision = ColorVision::Deutan;
+        let (a, b) = (count(&mut h, off), count(&mut h, deutan));
+        assert!(a == 0 && b > 20, "Deutan: {a} fixed-line pixels in Off's colour, {b} in Deutan's");
+    }
+
+    /// A mode's table reaches the CPU picture: the sketch states and axes it changes, and nothing
+    /// else (the light theme in Off is the engine's own colours).
+    #[test]
+    fn cpu_picture_follows_the_colour_vision_mode() {
+        use crate::theme::ColorVision;
+        let rgb = |c: Color32| Rgb(c.r(), c.g(), c.b());
+        let off = scene_palette(false, ColorVision::Off);
+        let rg = scene_palette(false, ColorVision::Protan);
+        let t = Tokens::themed(false, ColorVision::Protan);
+        assert_eq!((rg.sketch_projected, rg.sketch_locked), (rgb(t.sketch_projected), rgb(t.sketch_locked)));
+        assert_ne!(rg.sketch_projected, off.sketch_projected, "the red-green table changes projected lines in light");
+        assert_eq!((rg.axes[0], rg.axes[1], rg.axes[2]), (rgb(t.triad[0]), rgb(t.triad[1]), off.axes[2]));
+        assert_eq!((rg.sketch, rg.background, rg.grid, rg.body), (off.sketch, off.background, off.grid, off.body));
+        let by = scene_palette(false, ColorVision::Tritan);
+        assert_eq!(by.sketch_locked, rgb(Tokens::themed(false, ColorVision::Tritan).sketch_locked));
+        assert_ne!(by.sketch_locked, off.sketch_locked);
+        assert_eq!(by.sketch_projected, off.sketch_projected);
+    }
+
+    /// The mode is on from the next frame (theme, widgets, caches, `ui.render`), and Cancel puts
+    /// it back.
+    #[test]
+    fn colour_vision_mode_reaches_the_frame_and_the_view_caches() {
+        use crate::theme::ColorVision;
+        let mut h = crate::scenario::Harness::new();
+        h.app.home.open = false;
+        let keys = |app: &SolveApp| (scene_key(app), highlight_key(app));
+        h.call("ui.prefs", json!({"open": "Graphics"}));
+        assert!(h.widget("Colour vision").is_some() && h.widget("Mode").is_some());
+        let before = keys(&h.app);
+        h.call("ui.prefs", json!({"color_vision": "deutan"}));
+        h.frame();
+        assert_eq!(crate::theme::vision(), ColorVision::Deutan);
+        assert_eq!(Tokens::get(), Tokens::themed(crate::theme::is_dark(), ColorVision::Deutan));
+        let after = keys(&h.app);
+        assert!(before.0 != after.0 && before.1 != after.1, "both caches are keyed on the mode");
+        h.call("ui.prefs", json!({"button": "cancel"}));
+        h.frame();
+        assert_eq!((h.app.preferences.color_vision, crate::theme::vision()), (ColorVision::Off, ColorVision::Off));
+        assert_eq!(keys(&h.app), before);
+        // `ui.render` (the CPU picture) shows the mode too: a fixed sketch line in Deutan's value
+        // (in the light theme, where the red-green table changes it; the render follows the theme).
+        h.call("ui.prefs", json!({"theme": "light"}));
+        h.frame();
+        h.app.run("sketch.create", json!({"plane": "XY"})).unwrap();
+        let made = h.app.run("sketch.line", json!({"points": [[-30, -20], [30, 20]]})).unwrap();
+        h.app.run("sketch.constraint.fix", json!({"entity": made["created"]["curves"][0]})).unwrap();
+        h.call("ui.view", json!({"view": "top"}));
+        let path = std::env::temp_dir().join(format!("sc_colour_vision_render_{}.png", std::process::id()));
+        let near = |h: &mut crate::scenario::Harness, c: Color32| {
+            let r = h.call("ui.render", json!({"path": path.to_string_lossy(), "width": 400, "height": 300}));
+            assert_eq!(r["ok"], true, "{r}");
+            let img = image::open(&path).unwrap().to_rgb8();
+            img.pixels().filter(|p| p.0.iter().zip([c.r(), c.g(), c.b()]).all(|(a, b)| a.abs_diff(b) <= 8)).count()
+        };
+        let (off, deutan) = (Tokens::light().sketch_locked, Tokens::themed(false, ColorVision::Deutan).sketch_locked);
+        let (a, b) = (near(&mut h, off), near(&mut h, deutan));
+        assert!(a > 20 && b == 0, "Off: {a} fixed-line pixels, {b} in Deutan's colour");
+        h.call("ui.prefs", json!({"color_vision": "deutan"}));
+        h.frame();
+        let (a, b) = (near(&mut h, off), near(&mut h, deutan));
+        h.call("ui.prefs", json!({"color_vision": "off"}));
+        h.frame();
+        let _ = std::fs::remove_file(&path);
+        assert!(a == 0 && b > 20, "Deutan: {a} fixed-line pixels in Off's colour, {b} in Deutan's");
+    }
 }
 
 #[cfg(test)]
diff --git a/crates/ui-egui/tests/scenarios/colour_vision_setting.json b/crates/ui-egui/tests/scenarios/colour_vision_setting.json
new file mode 100644
index 00000000..0cb44845
--- /dev/null
+++ b/crates/ui-egui/tests/scenarios/colour_vision_setting.json
@@ -0,0 +1,25 @@
+[
+  {"note": "#778: Preferences › Graphics › Colour vision. A mode applies at once, Cancel puts it back, OK keeps it, Restore Defaults on Graphics resets it, and the window keeps its size."},
+  {"click": {"handle": "titlebar:preferences"}},
+  {"expect": {"prefs": {"dialog": "General", "color_vision": "off"}, "same_width": "prefs:window"}},
+  {"widget": "Graphics"},
+  {"expect": {"shown": "Colour vision", "prefs": {"dialog": "Graphics"}, "same_width": "prefs:window"}},
+  {"widget": "Off"},
+  {"widget": "Deutan"},
+  {"expect": {"prefs": {"color_vision": "deutan"}, "same_width": "prefs:window"}},
+  {"widget": "Cancel"},
+  {"expect": {"prefs": {"dialog": null, "color_vision": "off"}}},
+  {"key": "Comma", "cmd": true},
+  {"widget": "Graphics"},
+  {"widget": "Off"},
+  {"widget": "Tritan"},
+  {"widget": "OK"},
+  {"expect": {"prefs": {"dialog": null, "color_vision": "tritan"}}},
+  {"key": "Comma", "cmd": true},
+  {"widget": "Graphics"},
+  {"expect": {"shown": "Tritan", "same_width": "prefs:window"}},
+  {"widget": "Restore Defaults"},
+  {"expect": {"prefs": {"color_vision": "off"}}},
+  {"widget": "OK"},
+  {"expect": {"prefs": {"dialog": null, "color_vision": "off"}}}
+]
diff --git a/docs/book/src/guide/ui-tour.md b/docs/book/src/guide/ui-tour.md
index 92e80cd1..0b9de9d0 100644
--- a/docs/book/src/guide/ui-tour.md
+++ b/docs/book/src/guide/ui-tour.md
@@ -51,7 +51,10 @@
   to its top.
 
 Preferences (File › Preferences) hold the theme, the units of new designs, the mouse preset, the
-visual style and autosave. Help › Keyboard Shortcuts lists every key, and File › Keyboard
+visual style and autosave. Graphics › Colour vision gives the colours that carry a meaning (sketch
+states, axes, bends, analyses, icons) values for a weak red, green or blue sense: Protan, Deutan or
+Tritan. In a mode, the faces Draft and Accessibility Analysis mark as failing are striped too.
+Help › Keyboard Shortcuts lists every key, and File › Keyboard
 Shortcuts changes them.
 
 Navigation › **Smooth wheel zoom** is on by default. Turn it off to apply each wheel or
diff --git a/docs/control-protocol.md b/docs/control-protocol.md
index a3f955f0..387a6516 100644
--- a/docs/control-protocol.md
+++ b/docs/control-protocol.md
@@ -127,7 +127,7 @@ unit regardless of the design, pass an expression with one: `"value": "50 mm"` o
 | `ui.home` | `open?`: bool; `sample?`: index | the start page: show or hide it, open a built-in sample (once built); returns `open` and the recent designs |
 | `ui.shortcut` | `command`, `key?`, `replace?` | a command's key, or rebinds it (`""` clears; a key another command uses is refused unless `replace`) |
 | `ui.help` | `item?`: `about`, `shortcuts` (read only), `report` (opens a report draft for review), `crashes` (the Crash Reports window) | the version, commit, build date and diagnostic text |
-| `ui.prefs` | any of `default_units`, `nav` (`fusion`, `solidworks`, `inventor`, `alias`, `tinkercad`, `openscad`), `zoom_reverse`, `zoom_to_cursor`, `smooth_wheel_zoom` (default true), `trackpad_pan` (default true: two-finger scroll pans, pinch zooms), `orbit_cursor`, `look_at_anim`, `look_at_speed`, `middle_double_click` (`home` (default), `fit`, `off`), `msaa`, `length_decimals`, `angle_decimals`, `theme` (`dark`, `light`, `system`), `language` (`en`, `ja`, `de`, `ko`, `ru`, `zh`; see [localization](localization.md)), `ui_scale`, `up_axis` (`z`, `y`), `offer_stand_up`, `check_updates` (default true; [updates](book/src/guide/updates.md)); `open` (a page: General, Navigation, Keyboard Shortcuts, Design, Graphics, Sketch, Selection) opens the Preferences dialog there; `button`: `ok`, `cancel`, `apply`, `defaults`; `stand_up: true` stands up a just-opened Y-up file | sets preferences (kept between runs), returns them all plus `dialog` (the open page or null), `dark` and `stand_up_offer` |
+| `ui.prefs` | any of `default_units`, `nav` (`fusion`, `solidworks`, `inventor`, `alias`, `tinkercad`, `openscad`), `zoom_reverse`, `zoom_to_cursor`, `smooth_wheel_zoom` (default true), `trackpad_pan` (default true: two-finger scroll pans, pinch zooms), `orbit_cursor`, `look_at_anim`, `look_at_speed`, `middle_double_click` (`home` (default), `fit`, `off`), `msaa`, `length_decimals`, `angle_decimals`, `theme` (`dark`, `light`, `system`), `language` (`en`, `ja`, `de`, `ko`, `ru`, `zh`; see [localization](localization.md)), `ui_scale`, `up_axis` (`z`, `y`), `offer_stand_up`, `color_vision` (`off` (default), `protan`, `deutan`, `tritan`: colour vision modes, #778), `check_updates` (default true; [updates](book/src/guide/updates.md)); `open` (a page: General, Navigation, Keyboard Shortcuts, Design, Graphics, Sketch, Selection) opens the Preferences dialog there; `button`: `ok`, `cancel`, `apply`, `defaults`; `stand_up: true` stands up a just-opened Y-up file | sets preferences (kept between runs), returns them all plus `dialog` (the open page or null), `dark` and `stand_up_offer` |
 | `ui.capture` | `action?`: `capture`, `revert`, `cancel` | answers the Capture Position question (asked when a command starts or the design is saved while components were moved without capturing); without `action`, what waits |
 | `ui.window` | `action`: minimize, maximize, restore, toggle, close | what the title bar's caption buttons do (on Windows and Linux the application bar is the title bar); close asks about unsaved designs first |
 | `ui.agent_cursor` | `show` (bool), `speed`: a number from 1 to 5 (times the normal speed) or `"instant"` (no animation: the command runs at once and the pointer jumps to where it acted), `follow_camera` (bool); all optional | the settings. While the cursor is shown, `engine.execute` first glides to the command's toolbar button and to each pick, then runs and replies; later requests wait their turn. `"animate": false` on a call skips it |