Make a dark green plaid blazer and a white dress shirt your outfit choice if you're aiming for a neat, fashionable ensemble. To give your overall outfit a more polished aesthetic, add dark brown leather derby shoes to the mix. In the colder months, when warmth is paramount, it can be easy to surrender to a less-than-stylish look. However, this look is a vivid example that you totally can stay cozy and remain stylish at the same time during the colder months. Seriously stylish, this ensemble is mature enough for a 30-year-old.