Sam’s Brown and Blue Striped Shirt has thick brown (or possibly black) stripes by the buttons, and a thin blue stripe as a sort of vertical “connect the dots” line between the buttons. That’s a poor description – basically the shirt is blue and brown with good sized stripes.
In Home (1x09), Sam put on this shirt when he, Dean, and Missouri try to figure out what has infected his former ‘home’ (if it can be called that when he only lived there for the first 6 months of his life). He keeps the shirt on throughout the subsequent poltergeist/ghost encounter, but changes before the final goodbye scene.
In Nightmare (1x14), Sam starts wearing the shirt after the failed attempt at rescuing Roger Miller. He keeps it on while through the rest of the main action of the episode, but changes for the final scene.
In Hell House (1x17), Sam wears it while he and Dean are hanging around the motel researching after first encountering the Tulpa – he is still wearing it when they take off to confront the record shop guy about lying.
In Provenance (1x19), Sam wears it the day after they find the old dead woman in her house through to when he and Sarah battle the ghost.
In Bloodlust (2x03), Sam wears it for the entire episode – except for when he wears a suit to interview the sheriff and go to the morgue.
In Nightshifter (2x12), Sam is wearing this shirt for the entire time he is at the bank (it is underneath a security costume when he first arrives).
In Dream A Little Dream Of Me (3x10), Sam is wearing this shirt when he shows up at the hospital with the information about the dream root. He keeps it on until they successfully get Bobby to wake up.
In The Real Ghostbusters (5x09), Sam wears it at the end of the episode when he says goodbye to Chuck and Becky.
In Unforgiven (6x13), Sam wears this shirt after he escapes from jail. He keeps it on until they kill the Archne.
In Season 7, Time for a Wedding (7x08), Sam wears this shirt when he and Becky arrive in Delaware and RSVP for the reunion, and then have a “romantic” dinner at Becky’s apartment.