InterestingChickens
Free Ranging
Looks like it is a feather that is off colour. If you were showing him, you could cut the feather out up to the pin section of it. You would need to keep an eye on it and help him lose the feather if needed. Of course, you would want to do this several months before a show to give him a chance to grow it back. Hopefully it would then return to it's normal colour.