Wiring Color Codes Reference

Why this matters

Wire colors communicate the function. Wrong color used or misread = miswire = arc, short, dead circuit, OR fire. Different voltages + different countries use different codes. The field tech who reads the color cold makes faster + safer connections. This is the field card for US residential + light commercial.

U.S. residential 120V / 240V (NEC + custom)

Hot (line): BLACK most common; RED for second hot in 240V; sometimes BLUE OR YELLOW for switch travelers OR phase ID. Never white OR green - those are reserved.

Neutral: WHITE (always). GRAY in some commercial. Carries return current.

Ground: GREEN (insulated) OR BARE COPPER. Never carries normal current; provides fault path.

Switch leg / travelers: in 3-way wiring, often RED + BLACK (from 14/3 cable). Re-marked WHITE if used as hot in switch loop (older homes).

NEC color rules

Neutral must be: white OR gray.

Ground must be: green, green-with-yellow-stripe, OR bare.

Hot can be: any color except white, gray, OR green.

Re-marked (permanent identification with tape OR paint at terminations) if changing function: e.g., white wire used as hot in switch loop = wrapped with BLACK tape at both ends.

240V residential

Two hots + neutral + ground (3-conductor + ground; old 3-prong style) - phase out for new.

Two hots + ground only (no neutral; pure 240V like baseboard heater) - black + red + bare.

Modern 4-prong (NEMA 14): two hots (black + red) + neutral (white) + ground (bare OR green).

Older 3-prong (NEMA 10): two hots + bonded neutral/ground. Legacy.

3-phase commercial 208V / 480V

High-leg (208V from a delta system): ORANGE - measures 208V to ground while others measure 120V. Highly dangerous mis-identification.

DC + low voltage

12V DC (RV, marine, auto):

• Red: positive
• Black: negative
• Yellow OR White: switched / accessory

24V DC:

• Red: positive
• Black: negative

HVAC 24V control (covered in detail elsewhere): R (red hot), C (blue/black common), W (white heat), Y (yellow cool), G (green fan), O (orange reversing valve), W2/Y2 (stage 2).

Phone (POTS): blue/white = tip; orange/white = ring. RJ-11 jacks.

Ethernet (T-568B): orange-white, orange, green-white, blue, blue-white, green, brown-white, brown.

Doorbell: red + white (no standard; functional pair).

Garage door safety sensor: white + white-with-black stripe usually.

International color codes

UK + EU (post-2004):

• Brown: line (hot)
• Blue: neutral
• Green/yellow stripe: ground

UK (pre-2004):

• Red: line
• Black: neutral
• Green: ground

Australia + New Zealand: similar to UK post-2004 (brown line, blue neutral).

Canada (CEC): similar to U.S. NEC.

Note: customer with imported appliance may have foreign color code. Don't assume.

NM cable conductor counts

14/2 (NM-B): 2 conductors + ground. Black + white + bare.

14/3 (NM-B): 3 conductors + ground. Black + red + white + bare.

12/2 + 12/3: same as 14/x but #12 AWG (20A circuits).

10/2 + 10/3: same idea, #10 AWG (30A).

8/3 (with ground): 30A range OR 50A subpanel feeder.

6/3 (with ground): 50A range, EV charger.

4/3 + 2/3: 100A subpanel feeders + large appliance.

Specialty wiring

LV landscape lighting: 2-conductor 12V; usually black + black with stripe (one is positive).

Solar PV DC: red (+), black (-), green (ground).

Battery banks: red (+), black (-).

Speaker wire: typically RED + BLACK; or one striped + one solid. Match positive to positive.

Cable jacket colors (NM-B)

NEC 334 cable jacket color code (since 2001):

• White: 14 AWG NM-B
• Yellow: 12 AWG NM-B
• Orange: 10 AWG NM-B
• Black: 8 AWG NM-B + 6 AWG NM-B
• Gray: 4 AWG OR larger

Older cables (pre-2001) all white jacket; conductor size by ampacity label.

Common color-code mistakes

White wire as hot without re-marking (NEC violation; visual confusion). Green wire as hot (NEVER; reserved for ground). Hot phase wire on neutral terminal (potentially dangerous). Mixed up 240V hots (no harm in most cases since both are hot but matters for 240V control circuits + reversing motors). Re-marked tape removed (next tech misreads color). Orange high-leg ignored (240V where 120V expected; appliance damage). Foreign color code in imported appliance assumed U.S.

Working with old wiring

Knob + tube (pre-1940s): separate hot + neutral; no ground. Insurance + code issues; rewire.

Aluminum (1965 - 1973 some homes): silver-colored wire. Higher expansion; loose connections + fire risk. CO/ALR-rated devices required.

Cloth-jacketed BX (1950s): armored cable with cloth-insulated conductors; brittle. Often needs replacement.

Pre-grounded wiring: outlets only 2-prong (no ground). Modernize to grounded outlets OR retrofit GFCI for protection without ground wire (3-prong allowed under specific NEC).

Identifying live vs neutral on unmarked wire

Multimeter to ground: hot reads 120V; neutral reads 0V.

Voltage pen: lights up near hot, dark near neutral. Verify with multimeter.

Test before assuming: even if color looks right, never trust without testing.

Wire labels + tags

For panels + j-boxes: legible labels at every termination point + breaker. Standard format: room + function + circuit number.

Wire markers: at major splice points OR control panel terminations.

Sharpies, dymo labels, OR pre-printed tags.

Common phase-identification rules

For 240V circuits: doesn't matter which leg is which for resistive loads (heaters, dryers).

For motors: phase rotation matters; reverse 2 phases changes motor rotation.

For control circuits: phase ID critical (HVAC 24V control reverses on hot/common swap).

Truck stock for wiring color work

Electrical tape multi-color (black, red, green, white, blue), wire markers + labels, sharpie, multimeter, voltage tester, magnifier (for old + faded markings).

References

• NEC Articles 200 (neutral), 210, 250 (grounding)
• NEC 408 (panelboards)
• NEC 310 (conductors)
• NFPA 70E (workplace electrical safety)
• Mike Holt color-code resources
• Manuall internal: Wire Termination Types, Switches + Receptacles