|Image is from Andy M¢ on Flickr.com under a Creative Commons license|
This is Lenny, an Australian shepherd. He's one of the common colors in the breed: liver (red) merle with tan (copper) and white. Though this picture makes it difficult to tell, he has very noticeable merle markings. So, what's his genotype?
Since the base of Lenny's coat is actually black with tan points, he is expressing the tan point gene. Most of the Aussies you will see, especially from show lines, are tan point. This would make him atat tan pointed.
Next, the black in Lenny's coat has been turned to brown. This is due to the recessive liver gene and makes him bb liver.
The red in this dog's coat is also rather dark. Going with the theory that the Chinchilla locus controls red intensity, this would make him Ccch moderately dark red.
Lenny is also a merle. He doesn't show any of the signs that are characteristic of a double merle, and thus he must be Mm merle.
Lastly, the white that is seen on him is fairly minimal, but does appear to fall within what can be expected of a dog that is expressing Irish white. This would make Lenny sisi Irish white.
So, that's atat bb Ccch Mm sisi or liver merle with tan and white.