For an ensemble that's effortlessly smart and wow-worthy, consider teaming a green sweater vest with olive chinos. Balance out this look with a more relaxed kind of footwear, such as this pair of black leather sandals. Seeing as it's super hot outside, this look seems perfect and entirely summer-appropriate. Gents who wonder how to pull off cool casual outfits as you make your way through your 20s, you have your answer.