There are at least five theories that answer why zebras have black and white stripes. The first theorizes that the stripes are camouflage against predators in a woodland possibly. Another theory states that the stripes were to interfere with a predatory attack, and another relates to the stripes being a means for controlling body temperature.
Another interesting theory connects the coloration to social interaction among the herd. Finally, the last theory relates to the stripes getting in the way of a parasitic attack.
Up to this point, the last theory is the only one proven to have any validity. Scientists believe that the stripes are an evolutionary response to protecting zebras from diseases carried by flies. They came to this conclusion after looking at striping patterns across a few species, and comparing it with various environmental patterns.
They discovered that there was a connection between the intensity of the markings and the activity of parasitical flies.
However, scientists still believe there is more work to be done regarding zebras and their discoloration. Scientists know why stripes keep the flies away, but they have yet to discover why this is so.