A grey crew-neck t-shirt and dark green chinos worn together are the ideal combination for men who appreciate cool and casual styles. Play down the casualness of this outfit by sporting a pair of dark brown leather casual boots. This combination isn't a hard one to put together and it's summer-ready, which is important when it's boiling hot outside. Off-duty looks for stylish 30-year-old gents aren't actually that hard, as you can see here.