Too many colors?
Yes, exactly… there are advantages and disadvantages to both techniques of
applying and supplying material information. I can imagine a hybrid technique
that would have lists of "groups" of faces, independent of sub-object (element)
as well as possibly independent of material info, as well as a material list.
In this way, you could select groups of faces (even between sub-objects in
different objects) and apply colors to them directly, or indirectly via
material lists.