The chick in post 43 has a restricted down colour which resembles mottled pattern. I've also seen similar on the occasional het mottled chick. I can't see it actually being mottled as there would be no reason for a mottled bird to be near those breeds.
When I bred blue & green egg layers in UK the Cream Legbars, in particular, later in the season, would lay eggs which were so pale that they were embarrassing. They could only distinguished from white eggs when alongside. In my experience blue or green eggs get lighter & darker but I have never experienced one to go from blue to green or green to blue.