Go fun or go staid, but don’t go sporty unless you are an athlete. The safest course is socks that match the trousers. Please note that matching trousers is better than matching shoes, to offer continuity between the legs and ankle. Socks should be long enough to prevent hairs from peeking out.
Colorful and patterned socks are good too. This is now a standard expression of fettered revolt in the corporate gulag, where red is favored. Brand-wise, Paul Smith is king here, not mentioning various obscure brands, but you can get good ones at J. Crew and H&M. If you are in Beijing, check out Hotwind for fake Paul Smith.