For comfort dressing with a twist, marry a long sleeve shirt with a black and white crew-neck t-shirt. On the fence about how to round off? Complement your ensemble with white and black athletic shoes to switch things up. So as you can see, as a 40-something guy, you have a wide range of sartorial options.
This pairing of a long sleeve shirt and a black and white crew-neck t-shirt is outrageously stylish and yet it's casual enough and apt for anything. As for footwear, complete your ensemble with black slip-on sneakers. Perfect to convey that you're mature and confident enough to make your own sartorial choices.