They will cross breed, but then again mollies are so inbred generally anyway that even if you breed 2 that you think are the same some strange babies can occur, i have white and black mollies and some of their babies have come out part orange, just goes to show how inbred they are. whether your combination would look good is anyone's guess. But good luck trying.
Cheers, Karl
What do you get when you breed a sailfin molly with let's say, a lyretail or gold dust? Does it work? Do they turn out nice?