Ralph Brazelton is the only one that comes to mind. He was great in Orpingtons, but don't think he was a master in the Buff color genetics. Dan Honour has assumed that role in our generation with Tom Roebuck a close second. At 6:30 am with the kids' first day of school, no name comes to mind.
Call Ralph whatever you want, but he was a master of Buff Orps. No one is making him like he did yet.
Walt