Official AKC standards accept any Chihuahua color patterns. Preferences abound among breeders and owners, however. Those preferences combined with the available knowledge of color genetics result in common Chihuahua coat patterns that sometimes contradict genetic tendencies.
How Color Genetics Work
A basic concept of genetics is that there are dominant and recessive genes. When both types of genes are present, dominant genes are expressed over recessive genes in coat color. However, there are multiple sets of genes that interact with each other and contribute to observable coat color, like genes that make color either more saturated or duller.
For instance, black is the most dominant color, genetically speaking, in Chihuahuas, but a certain combination of genes might result in a blue Chihuahua, even if the dominant gene for a black coat is present. Solid black Chihuahuas are rare. There are at least three dominant genes that result in solid black. Because these genes are all dominant, they are actually easier to breed out than recessive genes are.
The Genetics Behind Different Coat Colors
Black and tan Chihuahuas (the color pattern seen in Dobermans) are the result of two of the most recessive genes in the entire set of genetic possibilities. There is a more dominant recessive gene that will mask black in a dog that would otherwise be black and tan. However, black and tan coats are not the least common. This coat color can be bred for, especially if a breeder knows the genetic traits of more than one generation of ancestry.
Some recessive coat color genes are indicated by physical traits other than coat color, like eye or nose color. The chocolate color gene is recessive but causes a brown nose and yellow eyes. No matter what color a Chihuahua’s coat is, you will know that dog carries a recessive chocolate gene if he has those traits. This is a handy fact for breeders who want to produce chocolate pups and don’t have chocolate adults.
True white Chihuahuas lack black pigment and are therefore very rare. White Chihuahuas have pale noses and light eyes, not to be confused with creams, which will have darker features that indicate color genes. Other genetic combinations might result in a dog who looks white but carries genes for a number of different coat patterns.
Merle, a coat color that has surfaced in the Chihuahua breed in the past twenty years or so, is not a true Chihuahua color pattern. The AKC does not recognize this coat color and a number of countries have banned registration of merle dogs. Merle is the result of a dominant gene from other breeds—Dachshunds, Shelties and Aussies, for instance—not an unusual physical expression of Chihuahua genes or a genetic mutation. That same dominant gene results in merle Chihuahuas; the accepted theory is that crossbreeding resulted in these dogs. Merle Chihuahuas are unusually large for the breed and have any number of serious health problems.