Araucanas and Ameraucanas and some Easter Eggers (Araucana or Ameraucana X other breeds) lay blue eggs. Green egg layers are produced when a blue egg layer is crossed with a chocolate egg layer (Barnevelder, Empordanesa, Maran, Pendesenca or Welsummer) and this specific type of Easter Egger is known as an Olive Egger. There is a great article on the differences between these chickens at http://www.the-chicken-chick.com/2011/09/ameraucana-easter-egger-or-araucana.html