Which colors are commonly used for hot conductors in US 120/240 V circuits?

• A. White or gray.
• B. Green or bare copper.
• C. Black or red (non-white, non-green colors).
• D. Blue or yellow.

Answer: (C)

In this area, color coding tells you what each conductor is doing. Hot conductors are the energized paths carrying current, and they’re kept distinct from neutral and ground by color.

For typical US 120/240 V circuits, the standard hot colors are black and red. Black is the primary hot, and red is used for a second hot leg (as in a 240 V circuit or a multi-wire branch circuit). These colors are purposely not white, gray, green, or bare, which are reserved for neutral or grounding. Other colors like blue or yellow can appear for additional hot conductors in more complex wiring, but the common hot conductors you’ll encounter in standard residential wiring are black and red.