I don't think it would be a "code" they would just supply all fighters with the same style gear. Maybe they have red and blue for the red corner and blue corner or maybe the colors themselves will be up to the fighter? Either way it's not going to be like a dress code where a fighters gear must meet certain specs. They would supply the fighters with the gear.
That sounds awful tbh. Every fighter would look the same, like they're a cast of the latest season of TUF or sth.