Farmer - your bull calf is far better than his sire. More bone, more muscle. Must have a good dam.
If you got even just 1 red calf, that tells you your bull is heterozygous black (one black gene & one red gene). A homozygous black bull of ANY breed, will ONLY throw BLACK calves. Now, they may be grey, brown, mousy, silver, etc. But they are black - diluted. And the dilution factor comes from the COW. A BLACK animal can NOT carry the diluter gene. The diluter gene is dominant over the black gene. If they are carrying the diluter gene - THEY WILL BE DILUTED if they are black factor cattle. Red cattle can carry 1 or 2 diluter genes and you may never know until you breed them to a black mate.