I found a wonderful way to help you in knowing all the different coat variations. Be warned there are a lot :)
The colors below are the only recognized breed standard colors. Any other color is not recognized by registering groups. ie dilutes, yellow, sable, & brindles. It doesn't mean your Aussie is a mix if he is any of the colors above it just means the dog would not be accepted in a show ring.
Here is a link to a great website along with photos.
The most common Aussie colors are highlighted in green
Self Black Black & Tan Black Bicolor Black Tricolor
Self Red Red & Tan Red Bicolor Red Tricolor
Self BM BM & Tan BM & White BM w/white & Tan
Self RM RM & Tan RM & White RM w/white & Tan
I hope this helps you get a better understanding of the beautiful kaleidescope of Australian Shepherd colorations.