We have raised some chicks and pullets and they have just started to reach maturity and lay (hooray!!) and the eggs have been mostly what we expected (they are light sussex's, black australorps, 2 australian pit game, 1 blue australorp, and 1 splash australorp). One of the pit games has been laying a small-ish very light tinted egg, and some of the sussex have started laying medium sized light brown to cream eggs, and this week we have started to see some of the younger pullets beginning to lay - at first someone started to lay light brown eggs, and now another has joined her laying BLUE eggs.
This came as a HUGE surprise. Three times now we have fetched blue eggs from the coop's nest boxes along with the others, and we cant figure out who is laying them! Our hens all came from reputable breeders who we are still in contact with and wouldn't have (knowingly) sold anything but a pure-bred bird. All of them have single combs, and plain faces, and their legs and feet are the expected colour for their breed - so no Araucana or Ameraucana characteristics that we can see... I'll go take some pictures, but I'm hoping someone can give me some hints for other clues to look for!