A navy blazer and light blue jeans are a combo that every modern man should have in his off-duty arsenal. Complement your getup with a pair of black canvas low top sneakers to immediately rev up the cool of your look. As you can see here, this ensemble is a really smart pick, especially for transitional weather, when the mercury is dipping. Guys who are curious how to rock cool casual dressing as you go into your 30s, this outfit should answer your question.