"Flag Brother"
Someone who hopper shopped, or had a field day in "donated," would assemble an outfit with many colors that resembled a "flag."
Usually it'd be a new boy and the term was probably as much a comment on their new boy status as it was on their fashion sense.
Sometimes, it seems, brothers would come from very poor backgrounds and the opportunity to parade in "new" clothes trumped any fashion sense they might have had.
It was derogatory and unkind but....heard it many times. I worked in 25-30 so would pass through donated area often (especially when it was poor weather).