A blue Chihuahua is a very rare and prized type of Chihuahua whose gray-blue color is the result of a recessive gene that causes the color of a black Chihuahua to become diluted. The recessive trait must be possessed by both parents to produce this type of Chihuahua.
Blue Chihuahuas are known to have the same temperament and traits as a standard Chihuahua. Breeding one takes a lot of effort, however, as one must breed different colors of Chihuahua, including fawn and brown, in hopes of getting one. Since the gene involved with the coloring is recessive, the chances are very low that a puppy has the gene, and even lower that the puppy has the full blue coat.