Marrying a red and black plaid flannel long sleeve shirt with navy jeans is an awesome option for a relaxed casual outfit. Not sure how to round off this ensemble? Rock brown suede chelsea boots to class it up. Can you see how super easy it is to look seriously stylish and stay warm when colder weather arrives, all thanks to looks like this? And if we're talking casualwear for 20-something gents, this look is perfect.