Through a quick look, multiple places say "any yellow colour is considered a major fault". It would seem as though if it wasn't possible, it wouldn't specify it?
I agree with this. Look for the oldest standard you can find. If its listed as a DQ color, then the color occurs naturally. For example in old lab/retriever standards yellow & liver have been DQ colors (also brindle & B&T) because they existed in the breed. Silver was never mentioned in lab/retriever standards because it was not in the breed.
Unfortunately most breeds recently standardized don't give those clues, for example the ukc plott standard doesn't mention buckskin & neither it nor the AKC standard mention merle.
