Pair a dark green blazer with black dress pants for a sleek polished outfit. If you're puzzled as to how to finish, a pair of black leather loafers is a never-failing option. Needless to say, it's easier to work through a super hot afternoon in a fresh outfit like this one. This getup illustrates that dressing your age and looking fashionable are not mutually exclusive things for a 20-year-old guy.