Hello Keith,

maybe intersting to understand vertex Colors:
http://math.hws.edu/graphicsbook/c3/s1.html
You don't need to read all, only scroll down to the colored triangle. The Colors are given only at the verticies - the shaders or programs interpolates between them.
The Wavefront files supports the same concept:
http://www.martinreddy.net/gfx/3d/OBJ.spec

MoI seems to write only General Colors/Materials in Object/Wavfront Files- so you have to Export to another Programm to use this Feature.

Have a nice day
Karsten