Short answer: NFPA 79, the Electrical Standard for Industrial Machinery (2018 edition), is the published US wire color code for control cabinets. Black carries ungrounded power, white the AC neutral, red the AC control, blue ungrounded DC, and green the ground. White with a blue stripe marks the DC common, and orange or yellow with a black stripe marks wires that stay live when the main disconnect opens. The NEC sets no colors inside a cabinet; the white and green rules you already use belong to building wiring. On a machine headed for Europe, IEC 60204-1:2016 takes over and moves two colors on the scheme.
Which standard owns panel wire colors
The NEC governs building wiring, and its color rules stop at the cabinet's line side. The article covering remote-control and signaling circuits assigns no wire colors, and nothing else in the code paints the inside of a machine panel. One rule you know does reach in: NEC 250.119 requires insulated equipment grounding conductors 6 AWG and smaller to be green or green with yellow stripes.
For the machine's own wiring, NFPA 79 is the schedule the industry publishes. UL 508A panel builders and machine shops wire to it, and a tech opening a US-built panel expects its colors; the NEMA enclosure types guide explains where the marking duties land alongside the color scheme. Outside the US, IEC 60204-1:2016 requires every conductor to be identifiable by marking or by color, drawn from a 12-color palette, and both standards accept a numbered ferrule or a colored sleeve as that identification. A scarce stripe color therefore never holds up a build.
On the power side, NFPA 79 carries its own rules when circuits share one enclosure, and the backplate and DIN rail layout guide shows how the color classes route across the panel. See the NFPA 79 rules for multiple motor circuits in one junction box.
The NFPA 79 color schedule
NFPA 79 assigns colors by circuit purpose — power, control, AC, DC — rather than by voltage number. A 480 V feed and a 240 V feeder both run black, and a 24 V DC control circuit runs the same blue a 125 V DC control circuit runs. Keep that distinction straight and the panel reads itself.
| Color | What it marks |
|---|---|
| Black | Ungrounded AC and DC power conductors: line and load feeders, motor branch circuits |
| White | Grounded AC conductor — the neutral of a 120 V control circuit |
| Red | Ungrounded AC control conductors |
| Blue | Ungrounded DC conductors: DC control, 24 V DC + to PLC I/O and relay coils |
| White with a blue stripe | Grounded DC conductor — the DC common |
| Green, or green with a yellow stripe | Equipment grounding conductor |
| Orange | Line side of interlocked equipment that stays energized when the main disconnect opens |
| Yellow with a black stripe | Conductors fed from outside the enclosure that stay live when the main disconnect opens |
Three habits keep the schedule honest. Reserve green for grounds alone; it is the first color an inspector checks on your panel. Let every power conductor run black and carry its identity on the ferrule instead. Treat orange and yellow-with-black as one family: wires that hold voltage with the door open.
What IEC 60204-1 changes on export machines
IEC 60204-1:2016 asks for wiring identifiable by marking or color and allows a palette of black, brown, red, orange, yellow, green, blue including light blue, violet, grey, white, pink and turquoise. Two colors carry reservations: green with a yellow stripe belongs to the protective bonding conductor alone, and light blue marks the neutral of an AC system or the midpoint of a DC one.
The working practice under the same standard sits close to NFPA 79. Red covers AC control circuits, orange covers ungrounded conductors that stay live after the main supply is isolated, and blue tones run on DC. Three deltas matter when a US-built panel goes abroad:
- Neutral: a European tech reads light blue as the neutral; on your panel, white is just another conductor color to them.
- Protective conductor: green alone is not the IEC marking; the conductor runs green with a yellow stripe end to end.
- Live-when-isolated: orange does the job NFPA 79 splits between orange and yellow-with-black.
None of that stops a white-neutral panel from working in Europe. It does mean the wire no longer tells the whole story to local service staff, so put the color schedule on the drawing and the panel reads correctly in both markets.
Where the color code earns its keep
A 480 V feed, a 120 V control circuit and a 24 V DC system share one steel box. Color is what tells you which lug is which at 2 a.m. A consistent scheme shortens the checks before troubleshooting; the IP rating chart and the grounding and bonding guide cover the rating and bonding marks on the same drawing, and the enclosure size guide sets the room the bundles need.
Two conductors in that panel stay hot with the door open: the orange interlock feed and any yellow-with-black supply from outside.
Watch the sensor pigtails as well. A 4-wire DC sensor runs brown and blue for its supply and black and white for its outputs, so the blue inside the cord is the return, not the 24 V hot your panel blue means. The 4-wire DC sensor color codes for brown, blue, black and white break the cord down lead by lead. Stripe colors can also be scarce on the shelf; when white-with-blue is not on hand, run solid white and sleeve each end blue, or carry the scheme on numbered ferrules — both standards accept marking as the identification.
Ordering the wire for a 480 V panel with 120 V control and 24 V DC
Take a typical machine panel as the worked example. The feed is 30 ft of 480 V three-phase in 8 AWG copper, good for 50 A at 75 °C. AC control adds 40 runs averaging 4 ft, with 20 neutral returns of the same length. DC adds 60 runs averaging 3 ft, split evenly between blue and white-with-blue. One 15 ft interlock feed arrives from outside the enclosure. Control wire is 18 AWG (0.82 mm²) PVC rated 600 V, the standard hookup stock. Swap in the run counts and lengths from your drawing before you order.
The rule in words: length each color from the drawing, add 25% for terminations, dress work and the next revision, then round up to whole spools of 25 ft, 100 ft or 500 ft. The arithmetic, per color:
- Black 8 AWG: 3 × 30 ft = 90 ft; 90 × 1.25 = 112.5 ft
- Green 8 AWG: 1 × 30 ft = 30 ft; 30 × 1.25 = 37.5 ft
- Red 18 AWG: 40 × 4 ft = 160 ft; 160 × 1.25 = 200 ft
- White 18 AWG: 20 × 4 ft = 80 ft; 80 × 1.25 = 100 ft
- Blue 18 AWG: 30 × 3 ft = 90 ft; 90 × 1.25 = 112.5 ft
- White-with-blue 18 AWG: 30 × 3 ft = 90 ft; 90 × 1.25 = 112.5 ft
- Yellow-with-black 18 AWG: 1 × 15 ft = 15 ft; 15 × 1.25 = 18.75 ft
That totals 543.75 ft of 18 AWG across five colors and 150 ft of 8 AWG in two.
| Color and gauge | Computed length | Order |
|---|---|---|
| Black, 8 AWG | 112.5 ft | cut from a 500 ft shop spool |
| Green, 8 AWG | 37.5 ft | same spool |
| Red, 18 AWG | 200 ft | 2 × 100 ft |
| White, 18 AWG | 100 ft | 1 × 100 ft |
| Blue, 18 AWG | 112.5 ft | 1 × 100 ft + 1 × 25 ft |
| White with blue stripe, 18 AWG | 112.5 ft | 1 × 100 ft + 1 × 25 ft |
| Yellow with black stripe, 18 AWG | 18.75 ft | 1 × 25 ft |
The decision turns on 100 ft computed per color. At or under 100 ft, one 100 ft spool covers the color with spare; under 25 ft, the 25 ft spool does it. Past 100 ft, round up in spools: 200 ft of red is two 100 ft spools on a one-off build, or one 500 ft production spool once the panel repeats as a family. The 25% spare is what pays for the revision that always comes.
What to put on the drawing and the order
Put three lines on the drawing. First, the color schedule: color against circuit class, exactly as the table above reads. Second, the marking scheme: numbered ferrules at both ends, plus the sleeve color for any conductor run in solid wire. Third, a note on the orange and yellow-with-black conductors stating that the panel holds voltage with the disconnect open, so the next tech reads it before the first measurement.
Then order the box around the wiring. Every external feed — the ones that earn yellow-with-black — needs a gland and a cutout at the position the duct layout wants, and the cutouts and glands guide sizes the entry. The box itself can be a custom stainless enclosure that takes material, size and every cutout from one piece, delivered in 10 business days from drawing approval. Route power and control bundles on separate paths per the backplate layout guide, land the grounds per the grounding and bonding guide, and mount the box at the height the enclosure mounting guide sets. If the panel carries a service receptacle, the 120 V receptacle article covers its code side.
Catalog dimensions to compare
Compare these catalog dimensions with your component layout. Open each enclosure for its rating, material and usable space, then check those specifications against your application.
| Enclosure | Material | Outside H x W x D / display | Rating |
|---|---|---|---|
| 60 × 36 × 16 in | 304 stainless | 60 x 36 x 16 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 48 × 36 × 16 in | 304 stainless | 48 x 36 x 16 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
| 60 × 36 × 12 in | 304 stainless | 60 x 36 x 12 in | Rated NEMA 4X / IP66 by the manufacturer; not UL listed |
Questions
Does the NEC set wire colors inside a control cabinet?
No. The NEC's white-neutral and green-ground color rules cover premises wiring; nothing in the code assigns colors to machine panel wiring. The published schedule is NFPA 79 (2018 edition): black for ungrounded AC and DC power, red for AC control, blue for ungrounded DC, white with a blue stripe for the DC common, and green for the equipment grounding conductor.
What color is 24 V DC control wiring?
Blue for the ungrounded DC conductor and white with a blue stripe for the DC common, per NFPA 79 practice. The color follows circuit purpose rather than voltage, so a 125 V DC control circuit runs the same blue. When the stripe color is off the shelf, solid white sleeved blue at both ends or numbered ferrules keep the scheme legible, since both standards accept marking.
Why are some panel wires orange or yellow with a black stripe?
Both colors flag conductors that stay energized with the main disconnect open: orange on the line side of interlocked equipment, yellow with black on feeds from a source outside the enclosure. A panel with an external 120 V interlock supply still measures 120 V on that wire after shutdown, so check for 0 V at orange and yellow-with-black conductors before touching anything.
What colors does IEC 60204-1 require on export machines?
Identification by marking or color from a 12-color palette: black, brown, red, orange, yellow, green, blue including light blue, violet, grey, white, pink and turquoise. Green with a yellow stripe is reserved for the protective conductor and light blue for the neutral or DC midpoint. Red marks AC control and orange marks conductors live after supply isolation, so the scheme maps closely onto NFPA 79.
Can marking replace colored wire when a stripe color is unavailable?
Yes. Both standards accept identification by marking, so numbered ferrules or colored heat-shrink sleeves at both ends carry the scheme — white sleeved blue for a DC common, for example. Keep one method per circuit class across the panel, and record it on the drawing's color schedule so the wire, the ferrules and the drawing agree.
