nice looking Brown RedsThose appear to be Brown-reds on the right end, and are possibly bantams. John will pedigree mate certain varieties and will move a cock from hen to hen on each day. This allows him to know exactly who is producing what.
There are experienced breeders who will breed Black into a variety that in general you shouldn't. It will be part of a very specific improvement project and the majority of chicks produced will likely be culled in the strictest sense of the term . Those cull will never leave their farm.
You wouldn't put a cock in with a hen you are conditioning for show.