I have never felt the 'black' requirement for cab is the wrong benchmark,the British system requires the meat to be sourced from Angus sired steers and heifers which means it is in fact Angus beef.
Years ago, when my grandfather bred Aberdeen Angus, they were fed on a high energy barley ration and marketed as Scotch Beef, all Scotch Beef was Angus. Using red breeds or hybrids especially in hotter climates makes more sense, and using a black Angus bull will satisfy the market requirements giving a black calf, while taking full advantage of heterosis.
Blackhereford, while the breeds I mentioned are minority breeds in the United States, they are major breeds in other countries, especially south of the equator, where function is more important than colour, the Tuli on an international scale is one of the fastest growing breeds in the world,having risen from total obscurity when first exported in 1977.