I would suggest that because she is a cross breed, it is a simple thing about her single gene for the blue green egg being deactivated by more dominant genes on the paired chromosome. I am sure she is not sick at all. I have an EE which did the same thing in the last year. The colour change for mine coincided with the pea comb turning into a multipoint comb. As the genes for pea comb and blue green egg sit next to each other on the one chromosome, the activation of the multipoint comb on the other chromosome may have deactivated or over-ridden the green egg gene.in mine the egg became palest buff and over time has darkened to be a light plum colour. I am glad I am not the only one who has experienced this. The egg on the left is her own daughter's egg who is only 1/4 Araucana and she is still laying blue green, whereas mother EE first laying blue green, then laying light buff, now pinky eggs is on the right is 1/2 Araucana. Go figure. Genes are fun, that's all.
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