Its interesting that they are developing the black coloration at such a different pace.
I just a few pics, taken today, of the three from the same batch that I threw into my 5G tank a few months ago. They are all the same age, in the same environment and yet have different amounts of black in them so far. These fish are only 7 months old, and its well known for Onxy percs to take more than a year to get all their black color.
this one was almost all orange up until a few weeks ago. Its a loner and the ones that have paired up chase it away.
this is the larger of the pair, and will be the female eventually. She has not developed the same amount of black as the other 2.
this is the blackest one I have so far. The male of the pair.
Here is a bunch of them at 4.5 months old.
Hope to the see the pictures of the others that are in your tanks.