Does the NEC require specific phase colors like brown-orange-yellow?

Mostly no — and this surprises electricians constantly. The NEC reserves white/gray for grounded conductors and green (or green/yellow) for equipment grounding, and requires ungrounded conductors to be identified by phase and system where a premises has more than one nominal voltage system (210.5(C)), with the means of identification documented or posted at each panelboard. The familiar black-red-blue (208Y/120) and brown-orange-yellow (480Y/277) sets are convention — near-universal, excellent practice, but chosen by the facility, not mandated colors. The exception that IS code: on a high-leg delta, the conductor with the higher voltage to ground must be marked orange (110.15).

Do conduits have to be labeled with voltage?

The NEC requires it in specific spots rather than everywhere — the general-practice layer comes from the facility. Good practice that inspectors and maintenance both love: voltage/system markers on raceways at panel exits, wall penetrations, junction pulls, and regular intervals in accessible spaces; circuit identification inside or on junction box covers; and the mandatory cases handled precisely — PV DC circuits carry their own explicit 10-ft reflective marking rule covered in the solar guide.

Where must the color scheme itself be documented?

At the equipment: NEC 210.5(C) requires the identification method for ungrounded conductors to be permanently posted at each branch-circuit panelboard or documented in a manner readily available. A printed legend label on every panel door — “480/277V: BRN-ORG-YEL · 208/120V: BLK-RED-BLU” — satisfies the intent, costs one B-595 label per panel, and ends every color argument for the life of the building.

Home GuidesConduit & Voltage Marking

Electrical Distribution

Conduit & Voltage Marking: What Is Code, What Is Convention

Ask three electricians whether brown-orange-yellow is required by code and collect three confident, conflicting answers. The truth is precise: the NEC reserves two color families, mandates one orange conductor, and otherwise requires that your identification scheme exist and be posted — the familiar palettes are convention doing code's paperwork. That distinction decides how you label an existing building whose wiring predates your standard.

Labeled electrical conductors and raceway identification in a distribution system

Figure 1: Identified conductors plus posted scheme — the combination 210.5(C) actually asks for.Color + label + posted legend

1. The Color Map, Honestly Labeled

The status column is the part worth memorizing — it tells you what an inspector can cite versus what your spec book enforces:

System	Colors	Status
208Y/120 V (and 240/120 single-phase)	Black · Red · Blue	Convention (near-universal)
480Y/277 V	Brown · Orange · Yellow	Convention (near-universal)
High-leg delta (240/120 4-wire)	High leg = Orange	CODE — NEC 110.15
Grounded (neutral)	White / Gray	CODE — reserved
Equipment ground	Green / Green-Yellow	CODE — reserved

Two different orange wires

Orange as a 480 V B-phase (convention) and orange as the high-leg delta marker (NEC 110.15) and orange as an NFPA 79 excepted circuit (machine wiring guide) can coexist in one facility. This is exactly why the posted legend at each panel is the load-bearing element — color alone was never the whole identification.

2. The Raceway & Box Labeling Layer

Post the color scheme legend on every panelboard door — one printed B-595 label per panel satisfies 210.5(C)’s documentation requirement and settles every future argument.
Mark raceways with system/voltage at panel exits, both sides of wall penetrations, and at intervals through accessible spaces — the same placement logic as pipe markers, applied to conduit.
Label junction box covers with the circuits inside (panel + circuit numbers). Thirty seconds at rough-in saves thirty minutes per future troubleshooting visit.
Feeder and service identification per your one-line: source, destination, and voltage on every disconnect and gutter — the wire numbering guide’s source-destination logic at distribution scale.
Mandatory special cases handled exactly: PV DC circuit marking per the solar guide, arc flash labels per the NFPA 70E guide, panel nameplate data per NEC 409.

Materials: B-595 vinyl for legends and raceway markers, B-427 self-lam for conductor-level ID, printed on an M610 at the cart or an i3300 in the shop.

Inside the enclosure, the rules continue

The NFPA 79 guide covers the machine-side conductor color convention, and the NEC 409 guide covers the nameplate the distribution feeds.

Read the NFPA 79 Guide