In general, border collies are medium-sized dogs with a moderate amount of coat, which is more often thick and prone to shedding. They have a double coat that varies from smooth to rough and is occasionally curled. While black and white is the most commonly seen color pattern of the border collie, the breed appears in just about any color and pattern known to occur in dogs. Some of these include black tricolor (black/tan/white), liver and white, and red tricolor (red/tan/white) which have also been seen regularly, and other colours such as blue, lilac, red merle, blue merle, brindle, and Australian red (also known as ee red, blonde, recessive red, or gold) which is seen less frequently. Some border collies may also have single-color coats.