I went to many Challenge Cup finals in the 90s and early 2000s, and it usually felt like a carnival atmosphere where fans of all clubs could wear their team's colours without any mither, just good-humoured banter. That atmosphere got less friendly in more recent times, though, and these days it's more likely that you are going to get grief from tanked-up idiots if you wear your team's shirt. That makes it much less fun, and is one of the reasons why I no longer go to big games as a neutral.