Sorry, didn't fully understand the question earlier.
Yes, black is black, blue cannot "hide" however you can get a really dark blue.
There was a thread discussing this some pages back, but. . . . blacks from a blue x black breeding, same as blacks from a blue x blue breeding, are still plain...
Black x White is what created blue long ago, making Jersey Giants one of the few to be originally blue (not introduced into the pool) however now, the blue color just simply works like any other BBS colored breeds.