USB A cables and ports have the inner plastic piece color coded. White for USB 1, black for USB 2, blue for USB 3 (5 Gbit/s), teal for 3.1 (10 Gbit/s). Red or yellow for always-on

Blue is the only one that's actually endorsed by USB-IF. For the most part USB-IF would prefer if everyone just used their little icons. Luckily manufacturers have a bit more sense and all follow the same color scheme (apart from the occasional black sheep)