So Im curious if this is possible but essentially what I want to do. Is lets say for a model that I have in 3ds max or Maya that is UV unwrapped I would like to. Select certain faces then fill those selected faces with a color. Then that color will appear as a diffuse on the unwrapped object. Is this possible?
Maya answer: You can assign a different colored material to the faces as needed, then use Transfer Maps to bake out an unlit diffuse map. Rendering workspace > Lighting/Shading > Transfer Maps
And in Max, you assign a multimaterial to your object. Fill the multi with materials with different diffuse color. Assign the coresponding material ID on the faces of your object. Bake the diffuse to a texture using the "render to texture" You could use vertex color aswell, but imo, it's less flexible.