This shirt is cut in the western style, does up with snaps, and is a very bold orange and blue plaid. Some might think it’s red, but I’ve actually held this shirt in my hands, and to me it looks very orange.
In About a Boy (10x12), this is one of three shirts that we see Dean wearing in the research montage at the beginning of the episode – he is wearing it when Sam comes into his room to tell him about the case and persuade him to leave the bunker.
In The Chitters (11x19), Dean wears this shirt when he is in the Bunker at the beginning of the episode.
In The British Invasion (12x17), Dean wears this shirt the morning after their drinking night with Mick.
In War of the Worlds (13x07), Dean wears this shirt at the beginning of the episode when they are in the Bunker.