@bruno3047, you're making assumptions about genetics that just can't be made without actual research (and even then, tbh). As far as I'm aware, we don't know why different color morphs exist in different areas. Obviously, genetics often plays a role, but that may not be the only contributing factor. A certain color may be more successful in an area, due to issues beyond genetics, which leads to that color being far more common. A certain color could be caused by the unique diet in that area. Do we KNOW that there are no gray bellied regals in the red sea? We know they aren't collected, but does that mean they don't exist, or just that they aren't collected? Especially considering that the yellow bellied ones sell for a higher price? You simply cannot make an assumption on the genetics of a fish, based purely on their appearance. That's not science. Science is doing the research to PROVE a theory, not just making assumptions about it. Don't make me get my scientist friend involved in this....
Side note, did you know that certain colors in certain animals aren't based on genetics at all? White markings in horses are often based on their position in the womb. Cloned horses can have totally different white markings! That's just random information that I find fascinating. Btw, I hope this doesn't come off mean, that's not how I intend it, but I just wanted to explain why it might not be as simple as putting two of the yellow bellied regals together, and getting 100% yellow bellied offspring. And the truth is, I don't know. I haven't tried it. But I can see possibilities that might result in other outcomes.