It sounds like some sports club has taken to wearing a “uniform” which makes it easy enough to spot them. You often have look at the rugger buggers for bad behaviour - I know when I was at university their bad behaviour was legendary. They once attended a beer festival en masse with big parts strung round their necks dipping a trotter into their pint before necking it.

edit: although you’d imagine they’d just change clothes, but they may be too tied to some made up ritual to do that