In a way that's mildly subtly intimidating, in order to bring out the Bruce in the other person. I seem to recall a study that showed that when randomly dividing sports players into wearing red jerseys and blue jerseys, the red team won a statistically significant larger percentage of the time - maybe a 1% edge or something from red?

So I'd go clean, straight lines on a strong red clothing, maybe with a little black mixed in, impeccable grooming, and otherwise just look you're going to win. If it makes someone say "fuck it" and not do the combat math in their head just one time because your opponent has mentally crumbled, then your odds are improved.