Here's the best reference I could find for the link between "pastel" coloration and developmental problems. It's thought that incubation temperature is the key.

http://books.google.com/books?id=zVXAQNK_4WwC&lpg=PT79&ots=nsYBEGQAOb&dq=designer reptiles pastel slider&pg=PT79#v=onepage&q&f=false