This is controlled by the celadon gene! I had a blue layer - she got eaten by a bear :S I have one chick from one of her eggs, and since it's a recessive I'm hoping within ~three months (gotta love quail - bird guppies) I'll have blue eggs again.
Good luck!

bird guppies
Some of mine that are 7 weeks now hatched out of blue eggs! I can't wait to see if they lay blue.
be sure to let us know! 

