Wear a brown waistcoat and grey dress pants if you're going for a clean, trendy outfit. You can get a little creative in the footwear department and tone down this look by rounding off with tassel loafers. You totally can remain cool and stylish under the oppressive heat, and this outfit is a good illustration of just that If you're wondering what you should wear as a 30-something Millennial guy, this combo is a good source of inspiration.