Quick Guide to Electrical Wire Color Codes

Electrical wires differ in many details, including wire type, material, thickness, number of wires in the cable, insulation type and thickness, etc.

When building an electrical system, it is very important to follow the electrical installation diagram/schematics - in order to differentiate wires in electrical systems, wires come in different colors, and knowing which color goes where is of utmost importance.

Updated: August 21, 2023.

Electric wire color code standards differ from country to country. As always, if unsure, hire a locally certified electrician (or company) to help You with wiring - better safe than sorry.

Unless otherwise stated, this article is about US wiring color codes.

Cable Sheathing Color Codes

Cable sheathing serves as a protective outer layer, ensuring that the inner wires are held together securely. Not only does it provide structural integrity, but the color of the sheathing also offers insights into the specifications of the wires it encases.

• White Sheathing: If you come across a cable with white sheathing, it means that the enclosed wires are of 14-gauge. These are designed for a 15-amp service and are frequently found in light circuits, as well as in certain receptacle circuits.
• Yellow Sheathing: A yellow exterior points to the presence of 12-gauge wires inside, tailored for 20-amp services. These are commonly used in circuits for GFCI outlets.
• Orange Sheathing: An orange-hued sheathing indicates that the cable houses 10-gauge wires. These are crafted for 30-amp services, catering to larger appliances like water heaters, air conditioners, and dryers.
• Black Sheathing: Black sheathed cables are reserved for even heftier devices demanding power between 40 and 60 amps. You're likely to find them used with ranges, air handlers equipped with electric heating elements, or even in connections leading to a sub-panel.

Note: for more detailed information, one can often refer to the printed text on the sheathing. This text provides specifics about the number of wires contained within and their respective gauges. Such markings give electricians and homeowners a clearer understanding of the cable's intended use and capacity.

Wiring Color Codes

Encased within the sheathing, wires display various colors, each signifying a specific function and, by extension, its associated safety implications.

The prevalent wire color codes encompass black, red, white, bare copper, green, and occasionally white or gray, and blue or yellow.

According to the National Electrical Code (NEC), only a few wire colors have strictly defined purposes. Specifically:

• White or Gray: Designated for neutral conductors.
• Bare Copper or Green: Intended for ground wires.

Outside of these mandated color guidelines, there are widely accepted industry standards that dictate the purpose of different wire colors.

Black Wires: Live Current/Hot

Black insulation consistently signifies "hot" wires, a standard in many household circuits.

In electrical terminology, "hot" refers to the wires responsible for transporting power from the electric service panel toward its endpoint, be it a light fixture or an outlet.

While it's acceptable to repurpose a white wire as a hot wire by marking it with electrical tape, the reverse – using a black wire as either a neutral or ground wire – is not advisable nor permitted. Black wires should solely be used for transmitting electrical currents - they are "hot".

Red Wires: Live Current/Hot

The red insulation on wires typically indicates they are "hot."

Often, red wires serve as the secondary hot wire in 240-volt setups. They also play a crucial role in connecting hardwired smoke detectors, ensuring that when one detector sets off an alarm, all interconnected alarms sound off in unison.

Additionally, in circuits where a light can be operated from multiple switches at different points, the red wire enables this multi-switch functionality.

White Wires Marked with Black or Red: Live Current/Hot

As mentioned before, when you see white wire insulation marked with black or red, it typically denotes its use as a hot wire rather than its conventional role as a neutral. Most commonly, this designation is made using bands of black or red electrical tape around the wire's insulation, though other colors might occasionally be employed.

For example, within a two-wire cable setup, a white wire might serve as the second hot wire for a 240-volt device or outlet. In such cases, this white wire should be wrapped several times with black electrical tape, indicating its deviation from a neutral function.

Bare Copper Wires: Grounding

Bare copper stands out as the prevalent choice for representing a ground wire. Unlike other wire types, bare copper doesn't come wrapped in plastic insulation; it remains exposed.

It's imperative for all electrical devices to be grounded. Should there be a fault, grounding ensures that electricity finds a safe pathway to the ground, preventing it from using the human body as a conduit.

These bare copper wires are affixed to various electrical components, like switches, outlets, and fixtures, as well as the metal frames or casings of appliances. Due to their conductive nature, metal electrical boxes require a ground connection. Conversely, since plastic boxes are non-conductive, they don't necessitate grounding.

Green Wires: Grounding

Green plastic insulation frequently denotes ground wires.

Electrical devices might also feature ground screws that are colored green. It's essential to ensure that green wires are solely used for grounding and no other function.

White or Gray Wires: Neutral

The presence of white or gray insulation on a wire typically identifies it as a neutral wire.

If inspecting a white or gray wire, check if it's wrapped with electrical tape, as this would signify it's being used as a hot wire. It's worth noting that over time, older wires might shed their electrical tape. Consequently, if you find a detached loop of tape within the box, it could have come from the neutral wire.

The label "neutral" can be misleading, suggesting the wire isn't electrified. However, it's crucial to understand that neutral wires can indeed carry current and pose a risk of electrocution. While "hot" wires (with black or red insulation) transport power from the service panel (or breaker box) to the appliance, neutral wires complete the loop by returning power to the service panel. Therefore, both hot and neutral wires are capable of causing shocks and should be handled with caution.

Blue and Yellow Wires

Both blue and yellow insulated wires occasionally denote hot wires when housed within an electrical conduit.

It's infrequent to encounter blue and yellow wires inside NM cable sheathing. Notably, blue wires are often utilized as travelers in setups involving three-way and four-way switches.

DC (Direct Current) Power Color Codes

DC electricity is typically used in automotive, marine, and solar applications - many people have already seen jumper cables and know that Red is Positive and the Black is Negative.

Since most cars have their negative battery terminal post connected to the chassis, "negative" and "common ground" are the same.

However, in many DC applications, there are also dedicated wires for "common ground," which is usually White or Gray. Thus, in DC applications, the wire colors are as follows:

• Positive (not a common ground): Red,
• Negative (not a common ground): Black,
• Common Ground: White or Gray.

Again, White or Gray (common ground) wire is not used in jumper cables, 12V battery chargers, and similar applications since the negative terminal port of the battery is connected to the car's chassis and acts as common ground.

If You are dealing with DC system which uses other colors, then, according to IEC, wiring colors are as follows:

• Common Ground: Green/Yellow (PE - Protective Earth).

Unearthed 2-wire DC electrical system:

• Positive: Brown (L+),
• Negative: Gray (L-).

Earthed 2-wire DC electrical system:

• Positive (negative earthed): Brown (L+),
• Negative (earthed): Blue (M), or,
• Positive (earthed): Blue (M),
• Negative (positive earthed): Gray (L-).

Earthed 3-wire DC electrical system:

• Positive: Brown (L+),
• Mid-Wire: Blue (M),
• Negative: Gray (L-).

Regardless of IEC recommendations, US recommended DC power circuit wiring color codes are:

• Common Ground: Green/Yellow, Green, Bare (PG - Protective Ground).

Unearthed 2-wire DC electrical system, as mentioned before:

• Positive: No Recommendations (Red (L+)),
• Negative: No Recommendation (Black (L-)).

Earthed 2-wire DC electrical system:

• Positive (negative earthed): Red (L+),
• Negative (earthed): White (N), or,
• Positive (earthed): White (N),
• Negative (positive earthed): Black (L-).

Earthed 3-wire DC electrical system:

• Positive: Red (L+),
• Mid-Wire: White (N),
• Negative: Gray (L-).

120/208/240 Volts AC (Alternate Current) Power Color Codes

120V AC, 208V AC, and 240V AC are typically found in residential objects and offices. Wire colors for these voltages are as follows:

• Phase 1: Black,
• Phase 2: Red,
• Phase 3: Blue,
• Neutral: White,
• Ground: Bare Wire, Green, or Green with Yellow Stripes.

277/480 Volts AC (Alternate Current) Power Color Codes

277V AC and 480V AC are typically used in industrial applications. Wire colors for these voltages are as follows:

• Phase 1: Brown,
• Phase 2: Orange,
• Phase 3: Yellow,
• Neutral: Gray,
• Ground: Bare Wire, Green, or Green with Yellow Stripes.

As one can see, phases of 120/208/240V AC wiring and 277/480V AC wiring do NOT share any color, except the "GROUND" - this is very important since just a quick look at the wiring tells the person enough information about used voltages and phases, significantly increasing the safety.

Advantages of Adhering to Wire Color Codes

Adhering to established wire color conventions in electrical endeavors is crucial for safety, meeting code standards, and streamlining future electrical tasks.

Utilizing incorrect color codes enhances the risk of electric shocks, compromising your safety and potentially jeopardizing your home, as improperly connected wires can lead to fires.

Recognizing the significance of electrical wire colors is also essential as the electrical code mandates that specific wires (like neutral and ground) adhere to a designated color scheme.

Having wires color-coded simplifies subsequent projects. Instead of wasting time discerning each wire's function, their roles are clearly marked, streamlining the process.

Note: Again, if unsure, hire a professional electrician (or company). Also, always check if the line voltage is present, if the electric breakers are in the Off position, etc. Better safe than sorry.