Wear a dark green plaid long sleeve shirt and chinos for a casual and stylish look. Go the extra mile and change up your outfit by wearing a pair of athletic shoes. This getup should encourage anyone who wasn't sure about wearing casual clothing after 40.
If the dress code calls for a semi-casual outfit, you can rock a navy trenchcoat and chinos. Add a dash of stylish casualness to by finishing off with a pair of athletic shoes. This pairing illustrates that as a 40-something gent, you have a wide range of styling options.