Budgie colors often change during their first few molts as a baby. What actually happens is that the pigment gets stronger, so yellows can get stronger and make blues fade to a different tone, for example. (I defer to the experts on this one, since I'm about as effective in a discussion of mutation as a pair of concrete socks).
I don't know if it's possible, by Sammy's wing and tail feathers have never grown back a different color (always white with a hint of grey). Jakob is just as cute as ever, even with her molt face!
Bethany and Jorge
Mini schnauzer, Watson (July 18, 2009)
Budgie, Sammy (April 13, 2014)
RIP Príncipe Pío