ArtRage has a realistic colour blending option that produces much better colour mixing than the standard RGB model used by most programs. ArtRage uses RGB as the default, because it uses less memory, but it is easy to switch on the Real Color Blending option in the tools menu. This makes it a good choice for people trying to mimic traditional painting!
There's a quick reference version of the colour palettes here:
Color Mixing in ArtRage
ArtRage is a natural media painting program developed by Ambient Design. You can learn more about it here
www.artrage.com