If the situation calls for an effortlessly sophisticated ensemble, make a dress shirt and black chinos your outfit choice. Complete your outfit with a pair of black leather casual boots for extra fashion points. This look is probably what you're looking for as a guy in his 40s.
For a casually stylish look, marry a dress shirt with black chinos — these items work well together. Tone down this ensemble by finishing off with white canvas low top sneakers. This ensemble is the perfect answer to the question of how to dress appropriately for your age after 40.