This casual combination of an olive crew-neck t-shirt and charcoal jeans is a tested option when you need to look cool and casual in a flash. Hesitant about how to complete this look? Finish with a pair of casual boots to ramp it up. Rest assured, this look will keep you snug as well as looking sharp in this transeasonal weather. And if we're talking casualwear for 20-year-old guys, this outfit looks great on most men.