If you don't like getting too predictable with your looks, opt for an olive long sleeve shirt and brown chinos. Complement your ensemble with a pair of dark brown leather derby shoes to easily amp up the wow factor of your look. Naturally, it's easier to work through a hot warm weather day in a light and breezy outfit like this. Think it's hard for 20-year-old gents to nail smart style? This pairing is hard proof of otherwise.