This page is written to help potential owners understand the genetic basis for the color of the dogs they see. It may also help breeders educate themselves on how the different colors occur given the genetic background of the parents that are to be bred. The full article can be read at: ASCA Color Basic Info
The basic body colors of the Australian Shepherd are Red and Black.
The Blue Merle is genetically a black dog carrying the merling gene(which breaks up the black color into a pattern of black patches on Grey).
The Red Merle is genetically a red dog carrying a merling gene (which breaks up the red color into a pattern of red patches on beige).
In the breed, there are non-recognized colors which are considered undesirable. These include sable, brown merles, brindle, gray/slate, diluted red and blond.
One basic rule of genetics is that gene pairs determine characteristics like color. One gene comes from each parent. With color, the dominant gene is the trait you see. The recessive gene is the trait you do not see unless it is paired with another, same recessive gene.
BLACK IS DOMINANT OVER RED!!!
Keeping this in mind, the rules for Aussie color are simple;
1. A dog with two black genes is black/black and appears black.
2. A dog with one black gene and one red gene is black/red and appears black.
3. A dog with two red genes is red/red and appears red.
BLACK/BLACK has only black genes to give, and all his pups will be black, although they may carry the red gene if the other parent contributed a red gene.
BLACK/RED will produce black or red pups. When it passes on its black gene, black pups will result. When it passes on its red gene, if paired with a red gene from the other parent, the pups will be red. These dogs are often referred to as red carriers or red factored.
RED/RED is a red. Two reds will produce 100% reds because there is no black gene to dominate. If a red is bred to a black/black all pups will be black but all will carry a red gene. A RED/RED bred to a BLACK/RED may produce either black or red puppies.
For the breeder, the only uncertainty is whether you have a black/red or a black/black dog because they look alike. If a black dog has a red parent they will ALWAYS carry a red recessive gene. If he is from two black parents, only test breeding will tell if he is a black/black or a black/red.
Ideal coloring on a blue merle should be a base color of black with patches of shades of grey. Ideal coloring on a red merle is a base color of liver or dark mahogany with patches of shades of lighter red.