Nature has a habit of making imperfectly beautiful pieces, and this happens to be yet another example. Black and white often mix in stones in unique ways, but they are hardly ever consistent. In Napoli White the black and white mixture make a semi-grey overtone to the stone due to the white crystals being sporadically separated by large specks of black so that no color overpowers the other throughout the slab almost forming a static-like image.
Give this piece a white or black base chosen based off of which overall color you'd wish to bring out more in the stone. But no matter what base you use, or how you use this slab, it will surely draw the eye in any design.