Which color of insulation is not permitted for the grounded conductor when using individual conductors in raceway?

The grounded conductor, often referred to as the neutral wire, must be identifiable and distinguishable from the other conductors in a raceway system. According to the National Electrical Code (NEC), the grounded conductor must have specific insulation color requirements to promote safety and prevent confusion during installation and future troubleshooting.

The color green, which designates ground or grounding conductors, and any variations including "green with three white stripes," are strictly reserved for grounding purposes. This means such coloring cannot be used for grounded conductors. The use of green or any similar designation for those conductors could lead to hazardous situations, as it may cause electrical workers or anyone making connections to misunderstand the circuit's designations.

In contrast, the colors white and gray are acceptable for use as the grounded conductor, identifying neutral conductors clearly. Black and red are typically used for hot (live) conductors and thus are not applicable as grounded conductors. The rules surrounding color-coding are crucial for maintaining safe and consistent electrical practices, ensuring that those working with or near electrical systems can do so with a clear understanding of the function of each wire.