A molly doesn't care what color the other mollies are. One male of any color with three females of any color will happily make babies of mixed coloration. The colors at the store result from human selections to arrive at those looks. Mollies, platys, and swords look similar but are different species so you'd want a male with females of the same species if you're breeding them.
If you don't want a bunch of fry, they get along fine as a sorority. I haven't tried a fraternity, myself, but single males are fine.