# Built-in colour books

AutoCAD `.acb` colour books built into the Select Color panel. Each file
carries its source and licence in its header comment.

| File | Book | Source and licence |
|---|---|---|
| `ral-classic.acb` | RAL CLASSIC, 216 approximate sRGB values | Adapted from Wikipedia, "List of RAL colours"; CC BY-SA 4.0 |
| `sikkens-4041.acb` | SIKKENS 4041, 1,624 colours | Open Colour Systems Collection 2.0, © 2015 dtp studio oldenburg (freieFarbe e.V.); CC BY-ND 4.0. Converted from the GIMP palette: same names, values and order, only the file format changed |

Values are approximate screen representations, not colour-binding
references. RAL is a registered trademark of RAL gGmbH and Sikkens of
AkzoNobel; these files are not affiliated with or endorsed by either.