Breed standards were created by the parent clubs (dedicated fanciers) of each breed. There are often 'incorrect' coloring or 'disqualifying' coloring in breeds that do occur on occasion, but the decisions were made that what constitutes such and such a breed would not include those. Sometimes, when breeds are introduced to new countries, different lines of thought are in place (ex. All Belgian breeds ~~ Groenandael, Tervuren, Malinois & Laekean ~~ are varieties of the same breed in all countries except USA, where they are considered separate breeds) and (ex. Keeshond come in silver/blk & red/blk in their native country but only the silver/blk is recognized in the USA.)
Other colorings may have been introduced in an accidental cross breeding (which is what happened in schnauzers ... I understand they were crossed with westies and then crossed back and that is where the white comes from). Then the 'white' is said to be rare, which it should be since it was never a coloring associated with schnauzers.
That is one of the reasons AKC introduced DNA testing. That kind of thing was difficult to police before. Now it is much more difficult to do such things and get away with and maintain AKC registration, but nothing can be done about the past.
Also, many names of breeds have nothing to do with the origination of the dog. Examples: Labrador Retriever is one (mentioned above). Australian Shepherd (not from Australian, it is an American developed breed of dog).
