Sam has another red polo shirt without any dorky pocket.
In Dead Man’s Blood (1x20), Sam wears it at the end of the episode when his Dad agrees that they should work together. He then keeps it on for the entirety of Salvation (1x21) and Devil’s Trap (1x22), and until after his visit to Bobby’s to check on the Impala during In My Time of Dying (2x01).
In Children Shouldn’t Play With Dead Things (2x04), Sam is wearing a red polo when Dean walks in on him watching Casa Erotica, he keeps it on until after they discover that Angela’s grave is empty and confront her father for the second time.
In Crossroad Blues (2x08), Sam wears it for the entire episode.
In Hunted (2x10), Sam is wearing it upon arrival in Lafayette, Indiana, when he scopes out Scott’s room. He is still wearing it when Ava tracks him down at the motel, but by the time the next day dawns, he’s changed.
In Hollywood Babylon (2x18), Sam wears it after the second death (death by giant fan) until Walter’s death.
In What Is And What Should Never Be (2x20), Sam is wearing it at the beginning of the episode when he is on the phone to Dean, and when he rescues Dean. He changes before the last scene of the episode, however.
In Fresh Blood (3x07), Sam wears it at the very end of the episode when he and Dean are fixing the Impala.
In Time Is On My Side (3x15), Sam wears it when they interrogate the demon at the beginning of the episode.
FATE: It was most likely blood-stained after the events of Devil’s Trap (1x22).