The quagga is an extinct sub-species of the plains zebra. The rear was brown without stripes and appeared more horse-like. The last one died in captivity in 1883. In 1984 the quagga was the first extinct animal to have its DNA partially sequenced. Only one quagga, a mare, was ever photographed alive. Picture taken at the London Zoo in 1864
A zebra is a member of the donkey family, and are often interbred with donkeys. All donkeys have a dark dorsal strip that runs down over their withers and down their shoulders; so the basic color is light with a dark stripe. Many horses have this marking as well, and some of the leopard appaloosas are marked similar to a zebra. It is hard to tell with a zebra, but my guess would be that they are light with dark stripes just like their donkey cousins, just more intense in color and stripes. Here is a picture of a donkey showing the dorsal stripe over the withers, and a beautiful ribbon leopard Appaloosa that resembles zebra markings.