While often ghosts (hypos) are lighter than normals, they're rarely as yellow as pastels tend to be, at least while young. Hypos retain semi-normal coloration, only without melanin, which causes black pigment to develop. Pastels still have melanin, and have true black on them, whereas the dark areas in a hypo aren't true black; they can be close, but they're never a true black, more of a grayish color. Pastels tend to be yellow and black, and ghosts are a pale orangey-tan color with dark gray.