All housings are color keyed.
This means gray housings will only plug into gray housings. Gray
housing won't plug into red or blue housings. Similarly, the
color key feature makes it possible for you to differentiate voltages
of your electrical circuits. For example, you do not want to plug a 36
volt battery pack into a 48 volt charger. Color keying your wiring will
help to prevent expensive and dangerous damage. Gray housings are by
far the most commonly used color. People who have only one voltage in
their work environment tend to use gray housings no matter what the
voltage is. However, if you have multiple voltages in your work
environment, we would strongly recommend that you follow the industry
color code guidelines listed below.