The multitude of colors is one
of the reasons that people become interested in this breed.
They are almost like snowflakes each and everyone is different.
Australian Shepherds come in four basic colors, Black, Red, Blue Merle, Red Merle.
The variances in between can be with or without the white and/or
copper markings. Then add in the legendary eye colors, that
can be full marbled, split, or flecked. All these combinations
make up our wonderfully unique breed.

Recommended site
for more information:
http://www.ashgi.org/color/