July 2021
USB-C was supposed to be the answer to the chaos that is charge and data cable compatibility. And to an extent it was. It unified ports and reduced the amount of cables and chargers I need to travel with. The cables themselves, however, turned out to be a mess. They come in many varieties with obtuse names, confusing markers, and unclear compatibility rules. Yet they all look exactly the same.
Here is a colour coding scheme for USB-C to USB-C cables to distinguish them by their use.
There are currently 8 types of USB-C cables defined. Benson Leung's post lists them and explains how they relate to power and data transfer rates. Drawing from that we can observe that cables differ in two dimensions. The first is the kind of data signalling a cable supports, and the second is the amount of current it can carry. Based on this we can give data signalling colours.
And give current ratings numbers of stripes.
Putting them together we get the full matrix of the 8 possible USB-C to USB-C cable types today.
| USB 2.0 | USB 3.2 Gen 1 | USB 3.2 Gen 2 | Thunderbolt 3 | |
|---|---|---|---|---|
| 3A | CC2-3 | CC3G1-3 | CC3G2-3 | CC3G3-3 |
| 5A | CC2-5 | CC3G1-5 | CC3G2-5 | CC3G3-5 |
The colour palette is taken from a 2011 article by Bang Wong designed with colour blindness in mind.
I tried this with nail polish on a few cables and this is what it looks like.
Different cables that look identical is not a new problem, and distinguishing them by colour is not a new idea. Crossover ethernet cables look exactly like straight through ones, but I recall they tended to be green. Some have even published standards for ethernet cable colours.
It did not take long before I started relying on the colour to not mix my cables up. Maybe the industry can one day start putting clearer markings for cable types. Or any markings at all. Looking at you, Apple.
Reach out if you have any suggestions or ideas for improving this.