Eye color
Eye color varies from brown to blue, and occasionally eyes of differing color occur; this is usually seen with merles. The ears of the border collie are also variable — some have fully erect ears, some fully dropped ears, and others semi-erect ears (similar to those of the rough collie). Although working border collie handlers sometimes have superstitions about the appearance of their dogs (handlers may avoid mostly white dogs due to the unfounded idea that sheep will not respect a white or almost all white dog), in general, the American Border Collie Association considers a dog's appearance to be irrelevant. Instead, it is considered more useful to identify a working border collie by its attitude and ability.