This combination of a dark green shirt jacket and a white crew-neck t-shirt epitomizes casual cool and casual menswear style. And if you wish to immediately dial down this look with footwear, complement this look with a pair of brown leather flip flops. Totally appropriate for warm hot weather afternoons, you can sport this outfit all season long. This getup demonstrates that as a man in his 40s, you have a wide range of dressing options.