...to keep it "Live", make six squares, and fill each of them with one of the colors you want to use. Make six Symbols out of these squares, then extrude your cube. Go to the Map Art option, and find your way through. When you apply any one of the symbols to any of the sides, and make it fit the whole side of the cube, voila! You can turn off/turn on the shading and invisible geometry functions to taste.
HTH
Bert