Ruyeex i suppose i can look into white, black, brown for ya though :3. 

The charcoal creates a border unlike chalk

Ruyeex
black = charcoal
white = chalk
brown = I didnt feel like making

Brown, Black, and White are missing

Ruyeex
Working on it slowly =D Soooon TM :3

It can also be applied to some mods but it's the same process but with some code but I don't want to stretch much since it's your mod.

Ruyeex sadly it does not work with cave paintings. i can look into what that would require, but it may also require code and if it does well i don't code xD

Edit: ok, so i looked and it looks like with a patch file i can add these colors to the vanilla cave arts (i just need to manually change the color of the cave arts as a texture file for each one =D)

I love the mod but does it work with cave paintings?