I think you may enjoy this article I put together on egg "hiccups" and their causes. Uneven pigmentation and related egg shell colour is covered under #7:
Thank you! Yes, I did enjoy the article and it was a joy to read. You referred me to your part of the article that explained pigment irregularities to better explain the blue band on the egg. I'm curious though, would that apply to araucana eggs? I was getting the impression that the pigment irregularities in your article was a hiccup in the 'painting' process of egg laying. Araucanas blue pigment is in the shell, not formed as a 'paint' on the top layer. So I'm thinking it may be apart of an irregular she'll development. Though the shell isn't thicker across the banded part as far as I can tell. Hmm.
Thank your for the article!