Here you have great example of a typical mask:
Here you have bigger description - sorry it is in German:
http://www.wolfdog.org/forum/showthread.php?t=1213
Anyway on the photo
1) red line means perfect mask
2) green line means NOT FULL mask (or sometimes BLURED (untypical)) mask
3) bordeaux line means NO mask (black mask)
You can judge ONLY adult dogs because also by some wolfes mask develop longer - the dog must have full mask not later than for the bonitation (~2 years).
But problematic is not only missing white colour but also too much white like here:
This can be good for American Wolves, Huskies or Saarloos but Czechoslovakian Wolfdog with such musk do not look typical...