I can't use more than one color in the same material in C4D
Moved from C4D a while back but It could be something to do with UV projection being set to a surface that isn't there.  Another reason for this could be flipped normals (in this case you would have to flip them back.  Have a look in the UV settings and change the projection type.  I'm not sure this is a lighting issue, you could always add a light to the scene but I'm under the impression there is ambient lighting by default.... Hope this helps.