Forgive me Ladies and Gentlemen . Not as far as I know but I'm not a GSD expert, I'm a mutt girlie myself but always had a white GSD on my wish list of dogs I will adopt one day!!! I'm sure someone more knowledgeable will be able to say more.
The issue is that **some** people breed for colour only (white,liver, blue) and not temperament, good hips etc - the 'standard' colour breeders (working and show people) tend to be more tied into the health testing schemes because to show or work to a certain level at some shows/trial here and most shows/trial on the continent, or be used as a breeding animal, the dog must have good health test results and obviously a sound temper - and you can't show whites, livers or blues.
So the gene pool is much smaller than for the 'correct' colours (black and gold/black and tan/sables of their various hues/blacks) and in my experience, and I do not wish to offend any white owners, I have never met one who's temperament I liked (all the ones I have met have been a bit timid/spooky) and I have never seen a white, liver, blue on the working field.