true red - e/e
It has often been said that the ACD only come in two colors --- ticked-black/tan or red.  With the help of
DNA testing, this has now proven to be untrue.  

An ACD may also be brown, called "chocolate", red (non-extension, e/e, red, instead of sable red) or
white.  Brown, red and white are not common colors.  The reason these colors are not seen very often is
because they are not actively being bred for, when produced - are not advertised for fear of reprisal from
other breeders and some puppies are actually put to sleep if they are any color other than that of the breed
Extension and Non-extension, refers to the extension of eumelanin over the dog's body. The dominant form, "E", is
normal extension. The recessive form, "e", is non-extension. When a dog is homozygous for non-extension (e/e), its
coat will be entirely red/yellow (phaeomelanin based). All dogs that have a brown (chocolate) coat will have at least
one "E" allele, because of the production of eumelanin.

The way to tell the difference between an Agouti red/yellow and an Extension (e/e) red/yellow dog -- is the Agouti
red/yellow almost always have some black/brown hair in the coat (usually around the ears and tail) and the
Extension (e/e) dog won't. Another way is the Agouti red/yellow must have at least one ("A^y") allele and can carry at
most one other agouti allele, the Extension (e/e) can carry any two Agouti alleles (not necessarily "A^y").
Comparison along side a normal "red"
(sable-ticked) ACD.  
Comparison along side two standard
colored littermates and two black (not
ACD's) puppies.