The Australian Cattle Dog (ACD), or simply Cattle Dog, is a breed of herding dog originally developed in Australia for droving cattle over long distances across rough terrain. This breed is a medium-sized, short-coated dog that occurs in two main colour forms. It has either brown or black hair distributed fairly evenly through a white coat, which gives the appearance of a 'red' or 'blue' dog. There are two accepted coat colours, red and blue. Chocolate and cream are considered to be faults. Blue dogs can be blue, blue mottled, or blue speckled with tan on the legs and chest and white markings and a black patch or 'mask' on one or both sides of the head. Red dogs are evenly speckled with solid red markings and similarly to the blue dogs can have a brown (red) patch 'mask' on one or both sides of the head and sometimes on the body.