If the EE hen laid blue or green eggs, chances are either 50% or 100% he has the gene.. depending on whether she was not pure or pure for the blue eggshell gene.
The blue eggshell gene is also closely linked to the pea comb gene.. BUT, not all EE have peacombs linked with the blue eggshell gene, as evidenced by EE laying brown or tan eggs being relatively common. So, even this will take some guesswork via test breeding or simply see what sort of offspring they throw.
Anyways.. if you want more naked neck EE just breed the roo to any hen that lays blue or green eggs and you are guaranteed to hit on several naked necked blue/green egger EE hens.
In other words, just be sure to use parents that have both the naked neck and hens laying blue or green eggs for each generation.
I would not recommend breeding peacombed NN with another peacombed NN as this might throw some birds that are "too naked" and may not handle very cold winters too well?
