From The Australian Shepherd Club of America (ASCA):
"The Australian Shepherd is a well-balanced dog of medium size and bone. He is attentive and animated, showing strength and stamina combined with unusual agility. Slightly longer than tall, he has a coat of moderate length and coarseness with coloring that offers variety and individuality in each dog. An identifying characteristic is his natural or docked bob tail. His gait is smooth, free and easily shows agility and efficiency of movement.
The Australian Shepherd is intelligent, primarily a working dog of strong herding and guardian instincts. He is an exceptional companion. He is versatile and easily trained, performing his assigned tasks with great style and enthusiasm. He is reserved with strangers but does not exhibit shyness. Although an aggressive, authoritative worker, viciousness toward people or animals is intolerable.
The only recognized colors are blue merle, red merle, solid black, and solid red. Blue merles and blacks have black noses and eye rims while red merles and reds have liver (brown) noses and eye rims. All colors may be with or without white and/or copper trim. Preferred height for males is 20-23 inches and for females 18-21 inches at the shoulder.
Australian Shepherds are considered by many people to be the ideal dogs. Their uncanny intelligence, whether herding livestock or being a companion is always at work. The Aussie’s loyalty and devotion are beyond question. If you are looking for a dog to be an active part of your work or play, consider the AUSTRALIAN SHEPHERD."