Is it a common trait for Americana hens to lay two eggs(One brown one green)

[black star]

Some years ago a friend of mine gave me a Americana hen and she laid two eggs(One brown one green),so some years later (Last year) I purchase some Americana hens and one of them are laying two eggs (One brown one green) just want to know; is it common or rare

 

[Ridgerunner]

Genetically it is impossible. A hen either lays a brown egg or a green egg, not both. So I'd say pretty rare.