It’s very rare for Sam to have simple plain coloured shirts – that’s usually Dean’s look. In S8, however, we see that Sam’s buys at least one shirt that might remind him of his brother. This shirt is blue (violet in some light), does up with buttons, and has a single simple pocket on the left breast.
In We Need to Talk about Kevin (8x01), Sam wears this shirt when he leaves Amelia’s house until after his first evening with Dean. He changes out of it before they leave Rufus’ cabin for Wisconsin.
In Hunteri Heroici (8x08), Sam wears this shirt from when the cake explodes at the old folks home until they defeat the bad guy at the bank.
In Citizen Fang (8x09), we see Sam wearing this shirt in a flashback to a very busy day, where he told Amelia in the morning that he wanted to fight for her, met Don later at a bar, and then told Amelia in the evening that he was leaving her – and did so. (Thus connecting the flashback to the first appearance of this shirt in 8x01 We Need to Talk About Kevin).
In Clip Show (8x22), Sam wears this shirt from the beginning of the episode until they get back from visiting the priest in St. Louis.
In Bad Boys (9x07), Sam wears this shirt when he and Dean go to the diner, after they believe they’ve solved the case. He wears it until the end of the episode.