Select Color and ribbon: ByLayer shows the layer's colour

ByLayer swatches were always gray. The Select Color panel's Current/New
band and info line now show the colour of the layer the colour is for
(the newest selected object's layer, or the current layer for new
objects); the ribbon's colour control and the ByLayer row of its colour
dropdown show the current layer's colour.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013rGmDUNr1hUf4zo1X3dak8

src/ui/ribbon/color_dropdown.rs

@@ -157,12 +157,14 @@ fn divider<'a>() -> Element<'a, Message> {
         .into()
 }
 
+/// `shown` overrides the swatch, so ByLayer can show the layer's colour.
 fn logical_row<'a>(
     color: AcadColor,
     cur_color: AcadColor,
     label: &'static str,
+    shown: Option<iced::Color>,
 ) -> Element<'a, Message> {
-    let (bg, _) = acad_color_display(color);
+    let bg = shown.unwrap_or_else(|| acad_color_display(color).0);
     let selected = color == cur_color;
 
     let swatch = container(
@@ -212,13 +214,15 @@ fn more_colors_row<'a>(active_color: AcadColor) -> Element<'a, Message> {
 }
 
 /// Builds the complete 5-section color dropdown panel element.
+/// `layer_color` is the current layer's colour, shown on the ByLayer row.
 pub fn color_dropdown_panel<'a>(
     active_color: AcadColor,
     recent_colors: &[AcadColor],
+    layer_color: Option<iced::Color>,
 ) -> Element<'a, Message> {
     // 1. ByLayer and ByBlock
-    let by_layer = logical_row(AcadColor::ByLayer, active_color, "ByLayer");
-    let by_block = logical_row(AcadColor::ByBlock, active_color, "ByBlock");
+    let by_layer = logical_row(AcadColor::ByLayer, active_color, "ByLayer", layer_color);
+    let by_block = logical_row(AcadColor::ByBlock, active_color, "ByBlock", None);
     let section1 = column![by_layer, by_block].spacing(2);
 
     // 2. 45-swatch Quick Pick Grid (5 rows × 9 columns)

src/ui/ribbon/mod.rs

@@ -174,6 +174,14 @@ fn position_ribbon_dropdown<'a>(
 }
 
 impl Ribbon {
+    /// The current layer's colour: what ByLayer looks like for new objects.
+    pub fn active_layer_color(&self) -> Option<Color> {
+        self.layer_infos
+            .iter()
+            .find(|layer| layer.name == self.active_layer)
+            .map(|layer| layer.color)
+    }
+
     /// The colour-book identity of the active colour, while the active colour
     /// is still the one picked from the book.
     pub fn active_color_name(&self) -> Option<String> {
@@ -1232,7 +1240,11 @@ impl Ribbon {
         win: (f32, f32),
         recent_colors: &[AcadColor],
     ) -> Option<Element<'_, Message>> {
-        let panel = color_dropdown::color_dropdown_panel(self.active_color, recent_colors);
+        let panel = color_dropdown::color_dropdown_panel(
+            self.active_color,
+            recent_colors,
+            self.active_layer_color(),
+        );
 
         let (align_right, h_pad, top) =
             self.dd_anchor(PROP_COLOR_ID, color_dropdown::PANEL_W, win.0);

src/ui/ribbon/widgets.rs

@@ -1167,7 +1167,12 @@ pub(super) fn render_large<'a>(item: &RibbonItem, ctx: &RenderCtx<'_>) -> Elemen
                 .width(Length::Fixed(PROP_W))
             };
 
-            let (color_swatch, _) = acad_color_display(active_color);
+            // ByLayer shows the current layer's colour.
+            let color_swatch = layer_infos
+                .iter()
+                .find(|layer| layer.name == active_layer)
+                .filter(|_| active_color == AcadColor::ByLayer)
+                .map_or_else(|| acad_color_display(active_color).0, |layer| layer.color);
             let color_row = prop_row(
                 crate::ui::color_select::color_display_name(active_color),
                 PROP_COLOR_ID,