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Electrical wires: what each colour means
White, green, bare, black, red, and the colour of the jacket: what the Code requires, what comes from the manufacturer, and why a colour isn’t proof.
In short
This guide explains what the colour of an electrical wire means in a home, and what comes from the Code or from the manufacturer. It doesn’t show how to connect anything: in Québec, that’s work for an electrical contractor.
- According to the Régie du bâtiment du Québec, an insulated neutral is white, or grey.
- Green is reserved for grounding and bonding; these conductors can be bare in several cases.
- The Code is generally silent on the colour of cable jackets.
- A white wire in a box is not necessarily a neutral.
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The colour chart
The Code doesn’t require every conductor to be identified by colour; it does so in certain cases, such as the neutral and ground. The rest comes from the cable manufacturer.
| Colour | What it indicates | Where the rule comes from |
|---|---|---|
| White | The neutral, when it is insulated | Code (Régie du bâtiment du Québec) |
| Grey | Also allowed for the neutral | Code (Régie du bâtiment du Québec) |
| Green | Reserved for grounding and bonding | Code (Régie du bâtiment du Québec) |
| Bare (uninsulated copper) | Grounding or bonding, allowed in several cases | Code (Régie du bâtiment du Québec) |
| Black | In NMD90 cable, the conductor that goes with the white one | Manufacturer (Nexans) |
| Red | In 3-conductor NMD90 cable, the second conductor alongside the black | Manufacturer (Nexans) |
These rules come from a technical interpretation published by the Régie du bâtiment du Québec in 2013, based on the 2010 edition of the Code.
White or grey: the neutral
According to the Régie du bâtiment du Québec, the neutral conductor of an installation, if insulated, is white; grey is also allowed.
Don’t go by appearances: a white wire in the box is not necessarily a neutral. When power goes to the light fixture first, the white wire can serve as the run to and from the switch.
And white electrical tape wrapped around a wire to make it a neutral isn’t recognized as a permanent marking.
A badly connected neutral, at the breaker or at the appliance, is among the causes the manufacturer Siemens names when an arc-fault breaker trips for no apparent reason.
Green and bare: ground
Green is reserved for grounding and bonding.
The Code allows these conductors to be bare, without insulation, in several cases.
What grounding does, and how to tell whether your home is properly grounded, is in our guide Home grounding.
Black and red: what the manufacturer does
In NMD90 cable from the manufacturer Nexans, the wires are black and white in 2-conductor cable, and black, red and white in 3-conductor cable, with a bare bonding wire.
There, white is the neutral and bare is the bonding conductor; black and red are the other conductors.
Unsure about a wire?
Don’t rely on colour alone. The price of the work is in the written quote, at no charge.
Send my quote requestJacket colour
The Code is generally silent on the colour of cable jackets.
At Nexans, the jacket of NMD90 cable helps you recognize the size: white for general-purpose No. 14, blue for No. 14 bedroom outlets connected to an arc-fault breaker, yellow for No. 12, orange for No. 10.
What the wire size changes on the breaker side is in our guide How many outlets on a 15 amp circuit?.
In older wiring
In a modern installation, the conductors are bundled in the same sheath. In knob and tube wiring, the black wire and the white wire run a few centimetres apart, each on its own supports.
The details are in our guides on knob and tube wiring and aluminum wiring.
Who is allowed to touch it
According to the Corporation des maîtres électriciens du Québec, no one may perform electrical work of any kind, in their own home or elsewhere for others, unless they are an electrical contractor.
That’s why this guide explains the colours without showing how to connect anything.
Our master electricians add, move or replace outlets.
Frequently asked questions
Is the white wire always a neutral?
No. When power goes to the light fixture first, the white wire can serve as the run to and from the switch.
Is white tape enough to mark a neutral?
No. According to the Régie du bâtiment du Québec, white electrical tape isn’t recognized as a permanent marking.
What does a yellow or blue jacket mean?
At Nexans, a yellow jacket indicates No. 12 cable, and a blue jacket, No. 14 cable for bedroom outlets connected to an arc-fault breaker. The Code itself is generally silent on jacket colour.
Can the green wire be used for anything else?
No. Green is reserved for grounding and bonding.
Can I replace an outlet myself?
No. In Québec, electrical work of any kind is reserved for electrical contractors, even for a single outlet.
Unsure about the wiring in your home?
Our master electricians add, move or replace outlets, and the price is in the quote.
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Sources
Consulted on October 30, 2026.
- Régie du bâtiment du Québec, Insulation colour of conductors or cable jackets (in French)
- Régie du bâtiment du Québec, Quality control of electrical installation work (in French)
- Nexans, CANADEX NMD90 Copper
- Corporation des maîtres électriciens du Québec, Electricity in my home, a safety matter (in French)