For a look that's super simple but can be modified in a ton of different ways, consider pairing a blue shirt jacket with a short sleeve shirt. Want to tone it down on the shoe front? Complete your outfit with a pair of white and black canvas low top sneakers for the day. As you can see here, it's super easy to look on-trend and stay toasty when colder weather comes, all thanks to outfits like this one. This ensemble shows how to keep killing in the casual fashion department as a 30-something Millennial guy.