Color requirements for wires in low-voltage distribution boxes

Low-voltage distribution box wires are color-coded to indicate their function: red or black for live, blue or white for neutral, green or green/yellow for ground, and other colors like yellow or blue for control or data signals.

Standard Wire Colors and Functions

U.S. Low-Voltage Wiring (NEC Guidelines):

• Black: Hot or live wire carrying current from the power source
• Red: Secondary hot wire or positive polarity in DC circuits
• White or Gray: Neutral wire returning current to the source
• Green or Green/Yellow Stripe: Ground wire for safety
• Blue: Often used for control signals or neutral in some systems
• Yellow, Orange, Brown: May indicate specific functions in complex low-voltage systems, such as switch legs, data, or communication lines European Low-Voltage Wiring (IEC 60446, examples from Germany and France):
• Brown, Black, Gray: Live wires (L1, L2, L3)
• Blue or Light Blue: Neutral wire
• Yellow/Green Twocolor: Ground wire
• Some countries may use Yellow, Green, Red for live wires with light blue for neutral, depending on local standards

Special Applications

• Lighting Control Systems: Blue may serve as neutral, yellow as switch leg or control signal
• Thermostats: Blue is typically the common wire (C), yellow controls the air conditioner
• Audio/Video Wiring: Red and white for right and left audio channels, yellow for video signals

Safety Considerations

• Always verify wire function with labels, circuit diagrams, or a multimeter before connecting
• Color codes may vary slightly by manufacturer or region, so consult local electrical codes
• Proper adherence to color coding reduces the risk of wiring errors, electrical shock, and equipment damage Understanding these color codes ensures safe, efficient installation and maintenance of low-voltage systems, from residential setups to industrial applications.