That is exactly what happens... Show people want to win! If darker birds are doing better at the shows, then those breeds are going to get darker... And the reverse is true, too. If lighter ones are winning, birds are going to get lighter. This can happen even if that wasn't why the darker bird won!Someone is welcome to correct me if I am wrong about this but Buckeyes were originally darker than RIRs. It could be that Buckeyes have become a bit lighter over the years, but I suspect that heritage RIR breeders of recent times have just taken the color closer to the buckeyes... and of course it could be both of these things.