I was a bird training show where the guy explained and showed how to train all types of birds, including pigeons,
I cannot remember the colours of discs on the boards he used, but as soon as he displayed them he got certain pigeons in by the colour displayed
He trained them to come and get fed as soon as they seen the colour they associated with feeding time, he let the audience pick the colours randomly, over the course of time we were there he was spot on every time, :-/ :-/ :-/