Why not wear a grey long sleeve shirt and a blue crew-neck t-shirt? Both of these items are totally functional and look cool when paired together. Add a pair of black leather derby shoes to the mix to effortlessly dial up the style factor of any ensemble. Come hot summer days you want to feel cool and sharp –– this outfit is ideal for this time. Surely a never-failing choice if we're talking dressing ideas for 30-something Millennial guys.