This shirt is a dark blue denim, and lighter on the inside (as you can see when he rolls up his sleeve). It has two breast pockets and dark buttons.
In Book of the Damned (10x18), Dean wears this from after Charlie calls until they defeat the Stynes at the cottage and Sam burns the book.
In The Bad Seed (11x03), Dean wears this shirt when they are back at the Bunker, having successfully captured Rowena. He wears it until the end of the episode.
In Our Little World (11x05), Dean wears this shirt at the end of the episode when he and Sam talk with Cas in the Bunker.