We have bred most of the yellow out of our herd by using darker herd sires and heterozygous black bulls on the red cows to darken the color some. Most of my customers prefer red or black, although I still get the od call looking for the gold color. We don't single trait select for color so if there is a good bull calf that is lighter red or gold he stays a bull. We do, however, try to eliminate the diluter gene so that we can mate our cows to black or red bulls.
One thing I learned very early in the purebred business is that everyone wants a low energy ration fed bull, but nobody buys them! I believe I feed ethically and have not had any problems with bulls breaking down because they were overfed. Those yearling bulls have to have some condition going in to do a good job in the breeding pastures. We target 3 lb per day rate of gain.