Olive egger roos genetics get complicated. Boy Howdy you can say that again!
You need to breed them back to a BLUE egg gene to get olive eggs( or a lot of olive layers) , and then they will be lighter then the egg he would have layed.
He will have
1 blue gene ( dominant)
1 white gene
1 brown spigot gene
So if your hen has 2 white genes ( dark egg layer) you will only get olive eggs when he passes his blue gene on. If you breed him to a girl with 2 blue genes, the eggs will be lighter ( his spigot gets diluted by there no spigot) but they have a chance of having double blue genes. To get olive eggers that consistantly lay olive eggs, you need birds that have 2 blue genes and a brown spigot gene. And since you cant TELL if they carry a white gene, its tough.
so, story is, its easier to get olive eggs from a wellie. Now that I understand
That being said, I have a f2 olive egger rooster I just got back ( muffs and pea comb, so he likely has the blue gene) that should ahve dark spigot and a green egg gene. If you breed him back to blue eggs he should still have a nice olive gene. he is 3/4 Marans with blue gene. If you do want one, hes around. I call him muffler 2.