Let's be real: buying an Olive Egger specifically for green eggs and getting light brown instead is the kind of fowl play that makes you question your life choices. The author here did everything right, picked up a nice mix of Marans, a Cream Legbar, and the promised green-layer, only to end up with a basket that looks like a boring beige brunch. We feel that disappointment deep in our yolk. And then, just to keep things interesting, three random blue eggs show up over nearly two months, like a hen is playing a very slow prank on them.
Now, here is our honest take: your Cream Legbar is probably the culprit, but not in the way you hoped. You said she's missing typical Legbar traits and laying green. That means she is almost certainly a mix, which functionally makes her another Olive Egger. A true Legbar lays blue, not green. So what you likely have is two Olive Eggers, one that lays a sad light brown (totally possible; they can be a genetic crapshoot) and one that lays green. As for those three mystery blue eggs, do not overthink this. Chickens do not have a monthly cycle beyond the daily egg, so you are not dealing with some bizarre hen period. The most practical explanation is that one of your birds is a late bloomer or an irregular layer who finally decided to show off. Seven weeks between blue eggs is not a cycle; it is a lazy hen testing the waters.
The practical takeaway here is a tough but necessary one: you cannot trust a label as final word. We have seen "Olive Egger" pullets grow up to lay khaki, beige, or even weird pinkish eggs. The color is a blend of the hen's genetics, and sometimes the genes just don't cooperate. If you want guaranteed blue, buy a pure Cream Legbar or an Ameraucana, not a mix. If you want green, buy from a breeder who shows you eggs from the parents. And if you just want a random blue egg to appear every few weeks like a cryptid? Apparently, you already have that going for you.
So what do we tell a reader who asks us about this? Stop chasing labels and start paying attention to the weirdo in your flock. That inconsistent blue egg layer is probably a young hen still figuring things out, or a older one who only lays on certain moons. Track her comings and goings; mark the eggs. If you figure out which bird it is, give her a terrible pun name like "Blue Suede Boo." And next time, buy from a breeder who shows you a photo of the hen's actual egg color. That is the only fowl play you can't get out of.