Egg color is genetic and will be determined by the parents/genetics of the hen. A dark green egg is a result of a blue egg layer being crossed with a dark brown egg layer. The most common blue egg layers are Ameraucanas, Legbars and Araucanas. Dark brown egg layers typically are Marans and welsummers. If you get one copy of blue and one copy of the dark brown gene, resulting eggs will be dark green. They are also called olive.
Chances are if a hen hatches from the egg you have it will not lay olive eggs. If the father is a blue egg producer, you will get a lighter green egg. If the father is a brown producer, you could get a medium brown producer or medium green. Do you know what kind of rooster fertilized the eggs?
One of my breeding goals is to get different colors of eggs from my pullets. I have an Australorp that lays brown eggs, but when the bloom dries they almost look pinkish-purple. I crossed her with an Ameraucana and hope to get a purplish egg color. You never know what will happen though. Plus I think I only got 1 or two pullets from them.