For something more on the cool and casual end, pair a white and black print crew-neck t-shirt with hot pink swim shorts. To infuse a more laid-back spin into your ensemble, throw a pair of brown leather flip flops in the mix. So if it's a warm summertime afternoon and you want to look sharp without exerting much effort, this ensemble will do the job in no time. Guys who wonder how to wear cool casual outfits as you step into your 30s, this outfit should answer your question.