Sam adds yet another blue plaid shirt to his wardrobe in S8. This shirt is quite plainly styled, and does up with simple white buttons rather than the snaps that Sam usually goes for. The darkest thickest strips run horizontal. I’m calling this Sam’s “Benny” plaid, since the first appearances take place in the only two episodes where Sam interacts with Benny.
In Blood Brother (8x05), Sam wears this shirt at the beginning of the episode when he and Dean arrive at the motel and Dean gets the phone call and leaves.
In Taxi Driver (8x19), Sam wears this shirt for the entire episode.
In Alex Annie Alexis Ann (9x19), Sam MIGHT be wearing this shirt when he and Dean bid farewell to Jody at the end of the episode.