It all depends on the genetic make up of the individual animal and the selective breeding put into the bloodlines by the breeder you bought your pastel from. There is no one answer for the questions above unfortunately.
~*Rich
1.0 100% Het Albino
1.3 Normal
1.0 Spider
0.1 Mojave
1.0 Pastel 100% Het Goldfinger
0.1 Pastel 66% Het Goldfinger
0.1 Pastel PH Goldfinger
While genetics can give you some idea it has not been 100% correct in determining the answers to your questions. While the NERD lemon has one of the best records as far as brighter pastels go it still is not a 100% record. I've actually taken a liking to the blond lines of pastel as they seem to mature with the least amount of browning out. Granted they start being a little darker on the spectrum of pastels to begin with.
These are our 2 year old blond girl. Pictures don't really do her justice though!