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
| System | Phase A | Phase B | Phase C | Neutral | Ground |
|---|---|---|---|---|---|
| 208V (3-phase wye) | Black | Red | Blue | White | Green |
| 480V (3-phase wye) | Brown | Orange | Yellow | Gray | Green |
| Delta (high leg) | Black | Orange (high leg) | Red OR Blue | White | Green |
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): white/blue = tip; blue/white = ring, both from the same pair. The orange pair is line 2. 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)
NM-B cable jacket color convention (industry-adopted since 2001, not an NEC requirement):
- 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 is the exception to the pattern. On a cable jacket, gray is far more likely to be telling you the cable TYPE than the size: UF-B underground feeder cable is gray. Do not read a gray jacket as "big NM." Read the printing on the jacket, which states the type, the size and the conductor count, and is the only thing on the cable that is actually required to be right.
Older cables (pre-2001) all white jacket; conductor size by the printing on the jacket.
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.
Ungrounded wiring: two-prong receptacles, no equipment grounding conductor in the box. Three ways out under NEC 406.4(D)(2): pull a grounding conductor and make it a real grounded circuit; replace with a GFCI receptacle; or feed grounding-type receptacles from a GFCI upstream. Both GFCI options come with a marking requirement people skip. The GFCI itself gets a "No Equipment Ground" label, and any grounding-type receptacle downstream gets both "GFCI Protected" and "No Equipment Ground." Without those labels the next person plugs in a surge strip that has no ground to shunt to and does not know it.
Identifying live vs neutral on unmarked wire
Multimeter to ground: hot reads 120V; an intact neutral reads near 0V. Do not turn that around into "0 volts means safe to grab." A neutral that is open anywhere upstream sits at full line potential through whatever load is connected, and it reads 0 only until you break the circuit. Treat a neutral as live until it is proven dead with the load disconnected.
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).
The single most-useful color-code habit is the RE-MARK ANY DEVIATION at both ends. Customer's old switch loop has white-wire-as-hot (legal pre-2011); WRAP IT WITH BLACK TAPE at both terminations. Customer's 14/3 has red + black as travelers in a 3-way; if you change to a different function, RE-LABEL at both ends. The next electrician 5 years from now sees your tape + knows what you did. No tape = confused tech + miswire callback + warranty issue. Re-mark always.
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