Black doesn't work the same way as white. All color patterns are based on the E (black) locus and variations of it, along with other genes that make barring, lacing, etc. The black gene can be really confusing to understand. I guess in a sense you can say that black masks other colors, but it's not really masking them, it's just that the basic black gene is dominant over other colors, so a bird can appear black, but have, for example, the birchen gene (e^r) hidden (E/e^r). If there are two birchen genes, you will get a birchen colored bird. To make it more confusing, it also depends on whether the bird is dominate for silver or gold, which works with the black gene to determine whether you are are seeing reds or silver on the black.
The white that masks other colors is recessive white. It takes two copies of the gene to keep any color from leaking through. If a bird is dominate white, then you will get splashes of black and red showing through.
