There are two types of basic colors in Aussies, red and black. Red merle and plain red are the two red colors, and blue merle and plain black are the two black colors. A column:

Colors: Red vs. Black

Red Colors	Black Colors
Red merle, red (tri, bi, self)	Blue merle, black (tri, bi, self)

Simply from experience, we know that black is the dominant color. Because of this, we assign black, a large B. Red will get a small b. When a Bb occurs, the dog is said to be red-factored (meaning it possesses the trait for reds). Here are all the combinations possible when dealing with these dogs. Remember, the top column in Punett squares are the sires, the left column are the dams.

Red vs Black Breedings

	Red sire	Red-factored Sire	Black Sire
Red dam	Genotype:100% bb Phenotype: 100% red b b b bb bb b bb bb	Genotype: 50% Bb 50% bb Phenotype: 50% black, 50% red B b b Bb bb b Bb bb	Genotype:100% Bb Phenotype: 100% black B B b Bb Bb b Bb Bb
Red-factored dam	G: 50% Bb 50% bb P: 50% black, 50% red b b B Bb Bb b bb bb	G: 50% BB 25% Bb 25% bb P: 75% black, 25% red B b B BB Bb b Bb bb	G: 75% BB 25% Bb P: 100% black B B B BB BB b Bb Bb
Black dam	G: 100% Bb P:100% black b b B Bb Bb B Bb Bb	G: 75% BB , 25% Bb P: 100% Black B b B BB Bb B BB Bb	G: 100% BB P: 100% black B B B BB BB B BB BB

As you now see, genotype and phenotype can be very different. Remember, the Bb's are still black, but carry red alleles, making them red-factored.