Like many aquarium fish today, platys are inbred to some degree, so, as henningc said, there's really no way to know what you'd get. Keep any fry that are attractive, and the rest, well, keep or feed them to something larger, or whatever you wish. If you don't want the fry to breed with each other, do keep the girls separate as soon as possible. They are sexually mature long before they are full size.
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