Balance is a big key to dressing well, and while I don't like hard-and-fast rules, it's a good idea not to identically match the scale and color of any two pieces in your outfit. Here the Swede creates a very strange looking connection between the white wide stripe in his polo and his white belt. Contrast
can look cool, but if it feels like you tried this hard to match your belt to your shirt stripe, you'll just end up looking awkward.
J. Lindeberg