Originally, the only blue egg gene present in the US or Europe came from Araucanas. That is where the blue gene in Crested Cream Legbars came from. Araucana is also the breed that brought blue shell genes to Ameraucanas and eventually EEs.
There is no other source of the blue shell gene outside...
It is a long list but I think everyone's list should be long. Starting with birds that fit your climate and then check off all your wants.
You'll only get olive eggs from crossing breeds. A dark brown egg breed with a blue or green egg breed.
My black Penedesencas fit all of those wants except...