I'm not trying to be rude either, but rather trying to educate.
What you are suggesting, Buff Goose Guy, would be SO highly unlikely. It would mean that the mutation would have to occur in one of the sex cells before dividing, the hen or drake with the mutation would have had to donate sex cells (eggs or sperm) from the time before and after the mutation (since not all of the offspring had it), and it would just happen to be the incompletely dominant blue gene mutation, out of the hundreds of thousands of possible genes.
Since the breeder has (or had) both blue runners and saxony ducks which carry the blue gene, I think that is a much more likely option. But I guess anything is possible.