Right, but the red could be in there however many generations back.
Basic example being if you are trying to breed australorps, which are black birds with a beetle green sheen, but you hatch a male with red leakage in the feathers, then you know somewhere along the line, it's not pure.
Also...
The red leakage on B is obvious. Are you seeing red leakage on B and D as well? I see a little bit of yellowing of the feathers on B, and sort of an underlying brassiness to D. Is that it?