Even if you get chicks from a breeder of fine quality BRs, some of those may not be up to par. Even two perfect parents, per standard, don't always produce perfection. But that perfect barring, the gravy boat chest, the nice head with a 5 pointer comb and that flowing tail on the rooster makes for some real eye candy!
So true, even the best parents can throw off-type and color offspring. That's why sellers of "show quality" eggs and chicks are not strictly truthful, as the chicks may not develop into show-quality at all. Really one of my pet peeves.