@SarahGen-- Yes, there is canine vitiligo. But loss of pigmentation in the dog's skin could be due to many different reasons. It could be a skin infection or disease, a vitamin deficiency or even related to an injury or the climate.
You should get it diagnosed and treated. Meanwhile, I would recommend getting omega 3 and zinc supplements for your dog. These are very beneficial for skin and hair. If the loss of pigmentation has to due with a deficiency, it might just do the trick.