Teaming a dark green crew-neck t-shirt with navy jeans is a savvy option for an off-duty look. Finish off your look with a pair of desert boots to serve a little mix-and-match magic. Keep this outfit ready to go come warmer weather, and rest assured, you'll save time planning what to wear on more than one morning. This pairing illustrates how to keep killing it in the casual fashion department as a 40-something gent.