Egg with two different shell colors???

[aart]

You could be right - I thought it odd that the green egg would fit so perfectly into the brown. This morning I cracked it open, and there was a small air gap at the end between the shells.

It is odd that they are so close in size...
...but the yolk smeared all over was a pretty good clue.
..and unlike the brown and white OP egg, brown and green can't happen in one egg.