Men probably wear solid or melange-colored trousers with odd jackets 99% of the time, and in doing so overlook the opportunity to mix things up a bit in a classic British way. By that I mean tweed trousers, like the ones in the photo from Rudolf Beaufays, a second-hand and vintage clothing establishment in Hamburg, Germany that I can't recommend too highly (the man has timeless taste).
As the photo shows, it's hardly necessary to only pair patterned trousers with navy blazers or gray cardigan sweaters, the safe choices that come first to mind. So long as the patterns are of a different scale, any combination of jacket and trousers that won't scare off the birds is perfectly appropriate for attendance at a casual outing like an American football game.
Next time you're looking to wear something a little different this fall, try checked trousers.