/back on topic
Black BBs are an option and the main desirable property for most people is also the property that sometime people don't realize can be a disadvantage - tracking your shots.
Black BBs are real stealthy. But if you mix them with white you can use the white as an occasional tracer round. My suggestion is to get a bag of black, try a full mag of black and see what happens. They try mixing in different ratios until you get a tracer mix you're happy with.
Just like muzzle flash in the real world, being able to locate your enemy by the projectile signature can be a tactical disadvantage. Black BBs are an OPTION that can help address that, but they are no better or worse than white for all other practical purposes.