I was about to say the same thing.

What it is is that both of those genes, the one for pea combs and the one for blue shells, are dominant, meaning that if a bird has just one allele of either, they will show that trait. Obviously there are other factors for both, as is evidenced in many Easter-eggers who have funky combs from having a single combed parent in the mix or by the varying shades of blue one can get in their eggs. The point here is if you cross a pea combed and blue egg laying bird to a non-pea combed and non-blue egg laying bird, more than likely the offspring will still have pea combs and blue egg shells because of the dominance of the genes. I think that's where this misconception comes from.
As far as why some may not lay green eggs, instead laying brown eggs, well, if we assume that the birds we order are first generation Olive eggers, then that is a cross between blue shells and non-blue shells. In order for the daughters of this cross not to have blue shells, the blue shell bird must only be carrying one allele for the gene, and so only half of his or her offspring in this cross will inherit the proper gene. This is more likely in the case of a cross between a Marans and an Easter-egger, but less likely (not impossible, just less likely) in the case of an Ameraucana or Legbar cross.
If we assume the birds received are
second generation Olive Eggers, getting brown eggs from the offspring of any cross becomes more likely. By this assumption, we are gathering that they are taking Olive Eggers directly from an Ameraucana, Legbar, or Easter-egger crossed to a Marans and then breeding them to other birds of similar lineage. Assuming the blue egger parent from the first crossing is carrying two blue egg alleles, then all of the daughters will lay olive eggs,
but they will also have only inherited one allele for the gene, as will the sons of that crossing. As a result, if those daughters and sons are then paired up, about a quarter of
their chicks will
not inherit the blue egg gene.
And if you can get through all that rambling, more power to you.

I would post pictures of my Meyer babies, but half of them don't seem to want to load anyway. :/