I learned that green eggs exist, just like Dr. Seuss' Green Eggs and Ham. Though I have seen images of ostrich eggs that have a green tone to the shell, passing some green chicken eggs today was quite a sight and surprise. Evidently they are laid by hens that have been crossbred.
There are chickens that lay blue eggs, such as the Ameraucana, Araucana and Cream Legbar. The eggs are blue because of a pigment called oocyanin these birds produce. When bred with a brown egg layer like a Rhode Island or New Hampshire Red, Sussex or Buckeye, a chicken that has genes for both blue and brown pigment is produced that can lay eggs with green shells. They are called Easter Egg layers and Olive Eggers.