For an off-duty ensemble with a modern finish, you can easily dress in a long sleeve shirt and aquamarine shorts. The whole look comes together if you throw in a pair of tan suede desert boots. So as you can see, as an over-40 man, you have a wide range of styling options.
Why not try pairing a long sleeve shirt with aquamarine shorts? As well as totally functional, both items look good worn together. Add a pair of light blue slip-on sneakers to this outfit and the whole look will come together brilliantly. Casual combinations for mature guys aren't actually that hard, as you see.