I have the silver/black kind with the orange stripe on the dorsal fin and the reddish bellies. I also have succesfully raised one batch of fry and have another fry being raised too.
Of my type, once the fry are about 3/4" long they trade their fry-spots pattern for horizontal lines.... this remains their coloring til they get to be a little over 1" long, and only at that time (approaching about half their adult size of 1-1/2" females, 2 to 2-1/2" males) do they start getting the reddish bellies, blue ventral fins (females mostly) and extended dorsal fin (males). Before that point it's difficult to sex them, even.