Graphite

https://github.com/brunolevy/GraphiteThree

How to add a custom colormap

1. Open GIMP and create a 1px-high image, as wide as you need. Color each pixel with the pencil tool.
2. Export the image as XPM into the Graphite source tree: GraphiteThree/lib/icons/colormaps/my_colormap.xpm
3. Edit the autogui.colormaps variable defined in GraphiteThree/lib/autogui.lua to append {'my_colormap',false}
4. Your colormap is now available in Graphite:

Note

This exact colormap can be found here : https://github.com/LIHPC-Computational-Geometry/automatic_polycube/blob/main/src/labeling_colormap.xpm