Why not dress in a light blue vertical striped long sleeve shirt and khaki chinos? As well as super practical, both pieces look nice paired together. Amp up this whole outfit with dark brown leather casual boots. And if we're talking dressing ideas for gents in their 40s, this outfit is a good look on almost any man.
This outfit with a light blue vertical striped long sleeve shirt and khaki chinos isn't super hard to put together and leaves room to more experimentation. You can go down a more classic route on the shoe front by slipping into black leather loafers. As you can see here, as a mature guy, you have a wide range of dressing options.