You can speed things up if you don't want to wait. Just yank that feather out, see what color it grows back. If it has less white on it, but still some, pull it again. Do that a few times and if it keeps growing back in white, I'd cull. I had several from Bev Davis lines with a LOT of white in them and it was a lot less after a few pullings, but not perfect. I elected to keep the blue roo because he is REALLY nice in a lot of other areas and I think it is worth it to keep him. When i have something better he will go the way of cull roosters.