The appearance features of USB 3.0

The appearance differences between USB 3.0 and USB 2.0: Observe the USB (itself) socket and the USB socket on the computer.

The color of the middle plastic piece: USB 3.0 - blue; USB 2.0 - black. Of course, the color distinction for some devices is not standardized. For example, some master control chips that support non-native USB 3.0 may not be blue. Some USB 2.0 devices such as MP3, data cables, etc. may be black or white plastic pieces.
If color cannot be used for distinction, you can also look at the number of interface pins. USB 3.0 has more pins compared to USB 2.0. In the Type-A interface, the inner part of the interface has 5 more pins, while in the Type-B interface, there is an additional piece on the top of the interface.