A turtleneck and dark green chinos are a good getup to keep in your daily off-duty fashion mix. Kick up the formality of this outfit a bit by finishing with a pair of tobacco double monks. This ensemble is most probably what you've been looking for as a gent in his 40s.
A turtleneck and beige chinos worn together are a perfect match. For something more on the classier end to finish off this ensemble, introduce tobacco double monks to the mix. This combo is the perfect answer to the question of how to dress appropriately for your age as you age into your 40s.