A black USB-A port usually signals a USB 2.0 connection, also known as Hi-Speed USB, with data transfer rates of up to 480 Mbps. But port colors are conventions, not an industry-wide standard, so a black port may not mean the same thing on every computer.
To identify a port reliably, check its markings and the manufacturer’s documentation. Labels and symbols may not provide a clear answer, and some ports have no identifying marks at all.
USB-A color conventions do not apply to USB-C. Most USB-C ports have no color, and any color on one may be cosmetic. USB-C ports also support a broad range of capabilities, making color alone an unreliable guide.
If you have confirmed that a black USB-A port is USB 2.0, it is generally suitable for everyday accessories such as keyboards, mice, flash drives, headsets and wired controllers. More demanding devices, including external hard drives and SSDs, may be much slower when connected to USB 2.0, particularly when transferring large files. Some drives may also fail to work if the port does not provide enough power.
USB 3.0 devices can generally connect to USB 2.0 ports, but they will be limited to USB 2.0 speeds. The reverse is also true: a USB 2.0 accessory can plug into a USB 3.0 port, but will not become faster. Matching lower-speed, lower-power accessories with USB 2.0 ports can leave faster ports available for devices that can benefit from them.
By common convention, white ports are typically USB 1.x, which supports speeds up to 12 Mbps, while black USB 2.0 ports reach 480 Mbps. However, manufacturers may use the same color for ports with different capabilities or choose other color schemes. When in doubt, consult the computer’s manual or the manufacturer’s website.
Sources: Engadget.