Zebras are considered black with white stripes, because their pattern is determined by pigment inhibitors that stop the black pigment that is natural to their skin from producing black fur in some areas. Also, zebras have dark skin underneath their fur.
Special skin cells called melanocytes produce the pigment that colors fur. Zebras release chemicals that stop some of the melanocytes from producing the pigments. As of 2014, scientists are unsure of exactly how the process works, but it results in white stripes on their otherwise black fur. Each zebra has a unique stripe pattern. The stripes reflect sunlight to keep the zebra cool and provide camouflage to help hide the zebra from predators.