- generations
One reason this feels sudden is that recessive genes can stay invisible for a very long time. A black dog can carry brown without showing any sign of it, and if that dog is bred to another black dog that does not carry brown, none of the puppies will be brown either. The gene is still there, just not visible.
That means you can go through several generations seeing only black coats and then unexpectedly get a brown puppy when two carriers are paired. This is why pedigrees matter and why experienced breeders keep detailed notes. Color outcomes are not random chaos; they are often hidden probabilities finally becoming visible.
- This does not mean the puppy is mixed
I have to say this plainly because it is always the first suspicion from people outside dog breeding: a brown puppy in a mostly black Newfoundland litter does not automatically suggest
