There are several breeds of chickens that lay blue-tinted eggs. Two of these, the Ameraucana and the Araucana or Rumpless Araucana, are the most commonly found in the United States. A third type which is widely available is called an Easter Egger.
The Araucana originated in Chile and was first brought to the United States in 1921. They are named for the Araucanian people who are thought to have originally bred them. They are also called South American Rumpless because they have no tail. They also have distinctive feather tufts on the sides of the face. Araucana are calm birds who adapt well to cold weather. They are good layers, and are content in confinement or as free rangers.
Purebred Araucanas do have one major disadvantage for those who breed their own stock. They have a recessive gene that will cause death in a quarter of the chicks while still in the shell.
The Ameraucana is probably descended from the Araucana, although there is some controversy about its origin. Unlike the Araucana which only lays blue eggs, the eggs of the Ameraucana range from pale green to pale blue. They are very adaptable to cold weather and have a generally calm temperament. They do well either as free range birds or in confinement.
Many chickens available in the U.S. that are marketed as Ameraucana or Araucana are actually Easter Eggers. The term Easter Egger means basically the same thing as mutt means to a dog. They are chickens that have mixed breed ancestors, but still tend to lay blue to green eggs. Some Easter Eggers will lay pinkish eggs as well. Because they are mixed breed, their personalities and laying capacities vary. They cannot be show chickens, but they are a good addition to a laying flock.
There are several other breeds that lay blue eggs. These breeds are much more common in England than in the U.S. but will hopefully become more available over time.
The Shetland is the rarest of these breeds. There are two sizes of chickens that are called Shetlands, a bantam and a full size. The larger size is thought to be related to the Chilean chicken. Because they are still rare in the United Kingdom, it is almost impossible to find them in the United States.
The Cotswold or Cream Legbar is another chicken from England. Although they come in a variety of colors, the only Cotswold that lays blue eggs is cream colored. They are extremely rare in the U.S., and are slowly making a comeback in the U.K.
Some Skyline chickens also lay blue eggs. About 80% produce blue eggs while the rest produce pink or cream shells. They are still fairly rare in the U.S. but are available. Skylines produce very large eggs and lay frequently. They adapt well to foraging or confinement and are very people-friendly. Skylines are also sometimes called Euskal Oiloa, Marraduna Basque or Basque Hens. There is at least one breeder in the United States who has hatching eggs available.