What Judy said. Pastel brightness/cleanness is a line-bred trait, so it's genetic--but not in the Punnett squares dominant/recessive sense of the term. Clean pastels are more likely to produce clean pastel babies, but there's no statistical certainty like there is with the pastel trait itself.
If you want your pastels to CONSISTENTLY produce bright offspring, you have to produce multiple generations, and hold back the only bright/clean babies for future breeding--the more times you select for BRIGHT pastel trait from parent to offspring to grand-offspring, the better your chances of later generations of bright pastels consistently producing bright pastel babies.
This is more like what is done in dog breeding.
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