What breed of chickens lay blue and green eggs?

There are no chickens that lay naturally blue or green eggs. The color of a chicken's egg is determined by the pigments in the shell, and there are no known breeds that produce pigments that result in blue or green eggs.

However, some breeds lay eggs that appear blue or green due to a different phenomenon:

* Araucana chickens: These chickens lay eggs with a pale blue-green shell, often described as "robin's egg blue." The color comes from a pigment called biliverdin, which is also found in the bile of animals.

* Ameraucana chickens: These chickens also lay blue-green eggs due to the biliverdin pigment. They are a relatively new breed developed from the Araucana.

It's important to note: While some breeds lay eggs that appear blue or green, the color can vary and may sometimes appear more gray or brown, especially in older hens.