Dean has a green shirt in S1 that looks quite nice on him (as green is wont to do). If he doesn’t have a jacket on, then he usually has the sleeves rolled up on it. Sometimes it looks grey, it all depends on how much of the colour spectrum the show lets us see.
Brand Information: Carhartt.
It first appears in Dead in the Water (1x03). Dean begins to wear it after the second death (drowning in the sink) until the very end of the episode.
In Bloody Mary (1x05), Dean wears it after the second death and while researching. He changes into something else for the side-trip to Fort Wayne and the confrontation with Mary, but then wears the green shirt again during the goodbye scene through to the end of the episode.
In Skin (1x06), Dean wears it when saying goodbye to Becky at the end of the episode.
In Bugs (1x08), Dean wears it when they are saying goodbye to the family they rescued at the end of the episode.
In Home (1x09), Dean wears it when he, Sam, and Missouri return to the house to try to figure out what sort of evil is haunting it. He keeps it on through the subsequent poltergeist/ghost encounters through to the very end of the episode.
In Faith (1x12), Dean wears it while he and Sam are doing research in the motel (Sam is on the laptop), and when they thwart the preacher’s wife.
In Route 666 (1x13), Dean wears it after the second death, takes it off momentarily when he needs to wear a suit to interview some random fellows on the pier, and then puts on the shirt again for the remainder of the episode except the final scene (and when having sex with Cassie).
In Nightmare (1x14), Dean POSSIBLY wears this shirt after the failed attempt to rescue Roger Miller for the remainder of the episode except for the very final scene.
In The Benders (1x15), Dean is wearing it at the bar when Sam goes missing, and keeps it on through the rest of the episode. The Benders burn a hole through the left front shoulder while they torture Dean.
In Something Wicked (1x18), Dean wears it for the entire episode, not taking it off once (that’s 3 days, with apparently no sleep either, I might add).
In Playthings (2x11), Dean is wearing this shirt on the morning that Sam wakes up with the hangover. He leaves it on for the rest of the episode.
In Abandon All Hope (5x10), the shirt makes its triumphant return. Dean wears it from the beginning of the episode until after the party and Bobby’s place. Dean may be wearing this shirt again at the end of the episode when they have a symbolic funeral for Ellen and Jo.
In Swan Song (5x22), Dean is wearing this shirt when he, Lisa and Ben, are seen having dinner through the window at the end of the episode.
In The Man Who Would Be King (6x20), Dean wears this shirt for the entire episode.
FATE: A hole is burnt through the left front shoulder with a hot poker in The Benders (1x15):
Yet, it miraculously healed itself (or, perhaps Dean had two identical green shirts and only one was ruined?)
In The Song Remains the Same (5x13), we see a young John Winchester wearing a similar shirt. It isn't exactly the same, the pockets are cut a little differently and the material seems to be heavier, but nevertheless, I thought I would mention it.