it's a subtle rainbow spread all over the page. it's different than the ones for birthdays, which are a rainbow within a single name.
the spread-out username rainbow are supposed to be like this on events only, but Staple picked up the habit to leave them like that for an extended period of time as the board isn't that active.
he had just disabled it after leaving it enabled for weeks when he remembered about the board's birthday, which counts as an event. so here we are.