The 'brown' color that makes the eggs go from the more blue towards an olive color is a secondary pigment added to the finished egg, sometimes this pigmenting system takes a while to fire up and work properly with new egg layers and in other cases this system might diminish a bit over the egg...
I only have a single EE hen that I acquired and a few EE roos, she lays a nice sky blue, from her and the roos that have the blue gene, I have bred out several different shades of green and olive...
Next year I'm going to hopefully expand my color range and breed some new colors with my new...