Black — hot
The standard hot wire — it carries current from the panel to the device. In a simple circuit, black is the one that's live.
THE WIRE GUIDE — CHICAGO
Electrical Wire Color Codes: What Black, White, Red, Green, and Bare Wires Mean
Wire colors are a language — and like any language, they have dialects. Here's what each color means in a house, what changes in a commercial building, and the one rule that overrides all of it.
RESIDENTIAL — 120/240V
The five colors in your walls
Standard North American residential wiring uses a small, consistent palette. Learn these five and you can read most of what's inside a house:
Red — second hot
The second hot leg in 240V circuits and multi-wire runs. You'll see it in dryer and range circuits, and as the traveler wire in 3-way switches.
White — neutral
The return path back to the panel. Code reserves white (and gray) for the grounded neutral conductor — it should never be used as a hot without being re-identified.
Green — ground
The equipment grounding conductor — the safety path. Green (or green with yellow stripes) is reserved for ground, period.
Bare copper — ground
Same job as green, no insulation. In Romex you'll see it alongside the black and white; it bonds everything metal back to the panel.
The white wire that isn't a neutral
There's one common exception worth knowing: in older switch loops, a white wire in a cable was re-purposed as a hot and should have been re-identified with black or red tape at both ends. Sometimes that tape was never applied — or fell off. So a white wire in a switch box isn't automatically a neutral. This is exactly the kind of thing the rule at the bottom of this page exists for.
THE DIAGRAM
Both palettes, side by side
The residential colors and the 277/480V commercial colors — the two systems you'll actually encounter:
COMMERCIAL — 277/480V
The palette changes in commercial buildings
Step into a commercial or industrial building running 277/480V and the colors shift: brown, orange, and yellow for the three hot phases, gray for the neutral, green or bare for ground as always. The logic is the same — hots, neutral, ground — but the colors are deliberately different so nobody confuses a 480V system with a 120/240V one.
A middle ground exists too: 208Y/120V commercial commonly uses black, red, and blue hots with a white neutral. And in conduit — which is how most Chicago-area commercial work is wired — hot conductors can be any color except the reserved ones (white, gray, green), so you'll see plenty of blue and other colors doing ordinary hot-wire duty.
The orange high leg
One color is actually required by code: in a 120/240V high-leg delta system, the high leg (the phase that reads 208V to ground instead of 120V) must be marked orange (NEC 110.15). It's the one color rule with teeth — because landing a 120V load on a 208V-to-ground leg ends badly.
THE TRAPS
Three ways color lies to you
The unmarked white hot
Old switch loops re-purposed white as a hot. The code calls for re-identifying tape at both ends — but tape falls off, and some installers never applied it. White in a switch box deserves the meter, not an assumption.
The old-UK red and black
Working on a building wired to older British convention? Their old colors were red for live and black for neutral — the mirror image of nothing in North America. (Modern UK uses brown and blue.) Imported equipment and old facilities are where this trap lives.
The "helpful" previous owner
DIY additions, miswired 3-ways, a traveler landed on the wrong terminal — residential wiring accumulates human error. Color tells you what the wire was supposed to be, not what someone did with it.
Which is why the banner on the diagram isn't decoration. Test before you trust: a non-contact tester for a first check, a real meter before your hands go in the box. Color is where you start looking, never where you stop.
Want the full map of every wire type these colors run on? The Wire Guide covers the whole territory, plainly explained.
Identified your wire and decided to sell it? We buy usable leftover rolls — anywhere in the country. Fast, free quote.
FREQUENTLY ASKED QUESTIONS
Wire color questions, answered.
What does the red wire mean?
In residential wiring, red is a second hot wire — used for 240V circuits (with black), multi-wire branch circuits, and as the traveler in 3-way switches. It's always a hot, never a neutral or ground.
Can a white wire be hot?
It shouldn't be, but it happens — most commonly in older switch loops where white was re-purposed as a hot and never got its re-identifying tape. Treat any white wire in a switch box as suspect until a meter says otherwise.
What's the bare copper wire for?
It's the equipment grounding conductor — the safety path that carries fault current back to the panel so the breaker trips. Same job as a green wire, just uninsulated.
What color wire is ground?
Green, green with yellow stripes, or bare copper. Those colors are reserved for grounding — you'll never legitimately find them used as a hot or neutral.
Why are commercial wires brown, orange, and yellow?
That's the conventional palette for 277/480V three-phase systems — deliberately different from residential colors so the two systems can't be confused. Gray is the neutral in that system.
Do 3-way switches use the red wire?
Yes — in a standard 3-way setup, the red (and sometimes black) conductors between the two switches are the travelers that carry the switched hot back and forth.
IRONCREST KNOWS WIRE
I know wire. That's how I know what it's worth.
Colors, letters, gauges — reading wire at a glance is the job, and it's how we know usable copper from scrap the moment a roll comes in. Know your wire, and you know what it's worth.