I see what you mean, while I did work with a limited color palette the lighting sort of blurred that fact. In my defense the rules seemed targeted towards a 2D sprite based game, so It was sort of up to interpretation for 3D mesh based games.
A toon shader wouldn't change much in terms of "colors" considering the meshes have smooth faces. So a gradient sort of lighting effect would still occur. Also in case anyone was wondering, I managed to make all the art assets for the game in less than an hour (Google Blocks is amazing :p ).