Buy a good number of RT frys(or flowerhorn or just purely almost any mid/large CA cichlid - not much of a difference), grow them all out. Sit and watch them grow almost every day for at least 1-3 hours a day without taking your attention off of them(pay attention to how they swim, their attitude aka body language, body shape, fin shape, head shape, and etc). You'll soon learn how to tell which one is female and which one is male without depending on any marking or venting. Use the surrounding of the fish including any fish in the tank to help you identify it as well.
In terms of fading, it may fade next week, it may fade when it hits 12 inches. I've known and seen 12" RT that aren't even mature yet and still acts like a hot head teenage who wimps out. Fading for RT can happen during its prime time. Only time will tell.