Bill I have thought about similar situations in the past. I have noticed that fish will more times than not try to pair up with the our strain/color. Think about all of the animals that can be imprinted. I think discus may be the same way. If they are parent raised the first part of their lives that are looking at their parents. When it comes time to spawn I think this makes them tend to look for their own kind. Not 100% of the time, but more of when they can.
-john