Bottlenose Dolphins are countershaded; that is to say that their ventral (stomach) side is a different color than their dorsal (back) side, for camouflaging purposes. While there are believed to be two species of bottlenoses and two subspecies of one of these (essentially making three total), they are all gray in color. Due to the aforementioned countershading, they are generally dark gray on top near their dorsal fin while they are very light gray to almost white along their underside.
More specificially, the black sea bottlenose dolphin is a gray that can vary somewhat among populations. Some are bluish-gray, some are brownish-gray and some are even nearly black. They are often darker on the dorsal side from the rostrum to the dorsal fin. On the other hand, the pacific bottlenose dolphin has the same coloring traits yet also possesses a black line from the eye to the forehead. Indo-Pacific bottlenose dolphins are more of a dark-gray with a belly that is lighter gray or nearly white with gray spots.