I've found pastels are tricky to pick out the best ones. Take this pair for example. They are both the same age (2 yrs) and are both from "dirty" lines (i.e. they're not NERD or Grazini, etc. - they're from mixed lines that had been crossed and then outcrossed). The male is the browner one and the female is the bright one. When I got them both, he was actually brighter and more vibrant than she was. But as you can see, she's VERY bright and he's browned out a lot. I'm hoping that she keeps her color and passes it on to some of her offspring.

But a year and a half ago when I got them, I never in a million years expected them to turn out the way they did.

Anyways, back to your original question, yes there are pastels that don't brown out. I do think they're in the minority though and that its hard to tell which ones will and won't when they're hatchlings.