I dont think anyone can truly answer those questions, I hatched out four pastels this year and every one of them has a different appearance, at 4 months old one has browned out as much as his 3 year old father, one male shows absolutely no signs of browning out, one is kinda in the middle of the pack, and the female looks like a super (which she definately is not) all were fathered by the same father that is holding his color better than most I have seen.

But in theory, selective breeding will give you animals that are best they can be.