Australian Shepherds come in two base colors, red and black , with or without copper (tan) or white markings, and can have the pattern called merle. Eyes can be brown, blue, amber (yellow), or a combination of these. Here are some definitions and examples of body colors and patterns:
Tris have a solid main body color, with copper and white trim. They may be any of the following combinations: solid red, solid black, red and white (Red Bi-color), black and white (Black Bi-color), red and copper, black and copper, red/copper/white (Red Tricolor), black/copper/white (Black Tricolor).
Merles have the basic color of red or black, as well as a mixture of lighter hair throughout the body. They may also have any combination of the copper and/or white trim. Merles have a much higher incidence of blue or marbled blue eyes. Puppies that carry two merle genes (called 'double merles', 'white Aussies', and sometimes 'lethal whites') can be born with too much white, and suffer varying degrees of deafness and/or blindness. While it can be striking, excessive white should never be considered desirable.
For an exhaustive field guide on Aussie colors and genetics, visit A Field Guide To Coloration of Australian Shepherds.