Oh darn... I got dupted... My ameraucana's are starting to show some birchen(?) Color bleeding through in their hackle feathers. The breeder I bought them from was very clear about the difference between an Easter egger and a "true" ameraucana. Can this happen in pure blues and blacks just as an unlucky coincidence?
Yes, it can happen. The trick to getting rid of it is first identify the females throwing the leakage, which means you have to grow out some males from them. Also, don't breed the males showing the leakage as they can pass that to their female offspring. Get rid of the females carrying it and don't breed the males showing it.