This shirt also has blue in it, I know, but to me the red and the white stand out more. It’s a hybrid cut. It has diagonal plaid on the shoulders, but not the pockets. It does up with white snaps.
Brand: Lucky Brand
In the Scorpion and the Frog (13x08), Sam wears this shirt in the final scene when he and Dean are drinking beers in the Bunker’s kitchen.
In Unfinished Business (13x20), Sam wears this shirt when they are preparing to go after Loki. He keeps wearing it until that business is finished.