The Blue egg gene is dominant, So if your EE hen lays a blue/green egg, then you know she carries at least One blue egg gene. For the EE Roo, have a very good chance he will have at least one blue gene.
Let's say They each have Only One blue gene. When crossed together your odds on the offspring will be 3 blue/green layers and 1 brown/white layer.
3:1 blue to non-blue
Of the blue layers, one of the three would be Homozygous for the Blue gene, meaning it had 2 Blue Genes, and that all offspring from that chicken would lay blue/green eggs; Even if bred to a regular breed of chicken.
If you luck up and your Roo is a Homozygous, your set. Of course, you can't tell by just looking at him. I'm pretty sure there isn't a dna test you can run. The old standard for checking if a breeding animal is homozygous, is to cross him on 10 non-gened mates, if all 10 offspring have the trait, then you are over 99% sure he is Homozygous. This is called a breeding test.
In your case, to check your Roo for Homozygous, you would breed him to regular brown/white laying hens, hatch 10 of those eggs, or enough to get 10 pullets. If all ten of those pullets lay blue/green eggs, then He is most likely Homozygous. Of course, if he has even one daughter who lays a brown/white egg, then he is Not Homozygous (he would be Heterozygous)
Kind of a long test with chickens.
Quickest answer is, If you only use blue/green laying hens, and your Roo is an EE with 2 EE parents, or better yet, from a hatchery who uses all Homozygous Roos, you'll get 75% or higher chance of blue/green laying offspring.
-Joycelyn
http://www.diamondjfarms.com/chickens/