The universal colour code in electronics maps specific hues to numerical digits (0-9), multipliers, and tolerances for passive components, while distinct regional palettes dictate AC/DC wiring polarity and phase. Whether you are reading a 5-band metal oxide resistor or tracing a 3-phase motor feed, the direct answer relies on identifying the standard in use: IEC 60062 for components, and either IEC 60446 or the NEC for mains wiring. Below is the complete, table-forward reference you need on the bench.
The Master Component Colour Code Reference
Component colour codes follow IEC 60062 standards. While surface-mount devices (SMD) have largely replaced through-hole parts in modern manufacturing, through-hole resistors and legacy film capacitors remain ubiquitous in repair work, vintage audio, and high-voltage power supplies.
Resistor Colour Code (4, 5, and 6-Band)
Read 4-band resistors from left to right, keeping the tolerance band (usually gold or silver) on the right. For 5-band precision resistors, the first three bands are significant digits, the fourth is the multiplier, and the fifth is tolerance.
| Colour | Digit Value | Multiplier (3rd/4th Band) | Tolerance (4th/5th Band) | Temp Coeff (6th Band) |
|---|---|---|---|---|
| Black | 0 | ×1 Ω | — | 250 ppm/K |
| Brown | 1 | ×10 Ω | ±1% (F) | 100 ppm/K |
| Red | 2 | ×100 Ω | ±2% (G) | 50 ppm/K |
| Orange | 3 | ×1 kΩ | — | 15 ppm/K |
| Yellow | 4 | ×10 kΩ | — | 25 ppm/K |
| Green | 5 | ×100 kΩ | ±0.5% (D) | 20 ppm/K |
| Blue | 6 | ×1 MΩ | ±0.25% (C) | 10 ppm/K |
| Violet | 7 | ×10 MΩ | ±0.1% (B) | 5 ppm/K |
| Grey | 8 | ×100 MΩ | ±0.05% (A) | 1 ppm/K |
| White | 9 | ×1 GΩ | — | — |
| Gold | — | ×0.1 Ω | ±5% (J) | — |
| Silver | — | ×0.01 Ω | ±10% (K) | — |
Legacy Capacitor Colour Code (Film and Mica)
Modern ceramic disc capacitors use a 3-digit printed EIA code (e.g., 104 = 100nF). However, older tubular, mica, and film capacitors use a dot or band system where values are read in picofarads (pF). The first two bands are digits, the third is the multiplier, and the fourth (if present) is voltage rating or tolerance.
- Black: 0 (Digit), ×1 pF (Multiplier), 16V (Voltage)
- Brown: 1 (Digit), ×10 pF, 20V
- Red: 2 (Digit), ×100 pF, 25V
- Orange: 3 (Digit), ×1,000 pF, 35V
- Yellow: 4 (Digit), ×10,000 pF, 50V
Rows People Get Wrong
The Gold/Silver Multiplier Trap: Hobbyists frequently misread a gold band in the third position as a tolerance indicator. On a 4-band resistor, if the bands are Brown-Black-Gold-Gold, the value is not 10 ohms. The third band (Gold) means multiply by 0.1. The calculation is 10 × 0.1 = 1 Ω with a 5% tolerance. Silver in the multiplier position means multiply by 0.01 (e.g., Green-Blue-Silver = 56 × 0.01 = 0.56 Ω).
5-Band Orientation: Precision 1% resistors often have a brown tolerance band that looks identical to the brown digit band. To find the correct reading direction, look for the wider spacing between the multiplier and the tolerance band, or use a digital multimeter (DMM) to verify the decade magnitude before soldering.
Regional Wiring Standards: IEC, NEC, and Legacy UK
While component codes are globally standardized, mains wiring colour codes are strictly regional. Applying the wrong standard can result in a fatal shock or a catastrophic short circuit. Always verify the local standard before terminating any cable.
| Wire Function | IEC 60446 (EU, UK, AU, NZ) | NEC (US & Canada) | Old UK (Pre-2004) |
|---|---|---|---|
| Protective Earth (PE) | Green & Yellow | Green, Green/Yellow, or Bare | Green & Yellow |
| Neutral (N) | Blue | White or Grey | Black |
| Line 1 (L1 / Hot) | Brown | Black | Red |
| Line 2 (L2 / Hot) | Black | Red | Yellow |
| Line 3 (L3 / Hot) | Grey | Blue | Blue |
What this means in practice: In North America (NEC Article 200 and 210), the neutral wire must always be white or grey, and the earth ground must be green, green/yellow, or bare copper. The "hot" wires are black, red, or blue. In Europe and regions adopting IEC 60446, the roles of black and blue are completely swapped compared to the US: blue is neutral, and black is a hot phase.
Under NEC rules, a white wire in a 2-wire switch loop is used as a "switch leg" (a hot wire returning from the switch to the light). Code requires this white wire to be re-identified with black or red electrical tape at both ends. In older homes, installers frequently skipped the tape. Never assume a white wire is neutral in a switch box; always test it with a non-contact voltage tester and a meter.
Safe Interpretation of Faded Markings and Common Traps
Components and wires degrade. UV exposure, heat from adjacent components, and chemical flux residue alter the visual appearance of colour codes. Relying solely on visual inspection in degraded equipment is a primary cause of bench and jobsite errors.
Reading Sun-Baked and Heat-Stressed Resistors
Carbon film resistors subjected to prolonged heat often experience colour shifting. The red band frequently oxidizes and fades to resemble orange or brown. Conversely, blue bands on metal oxide film resistors can darken to look violet under high thermal stress.
- Isolate the component: Desolder at least one leg of the resistor from the PCB. If you measure a resistor in-circuit, the DMM will read the parallel equivalent resistance of the surrounding network, giving you a false low value.
- Clean the body: Wipe the resistor with 99% isopropyl alcohol (IPA) to remove darkened flux residue that masks the true band colours.
- Measure and reverse-engineer: Read the DMM value, then work backward through the standard E-series values (E12, E24, E96) to confirm the faded bands. For example, if your faded resistor reads 4.6 kΩ, it is almost certainly a nominal 4.7 kΩ (Yellow-Violet-Red) that has drifted due to age, rather than a 4.6 kΩ precision part.
Dealing with Faded Mains Wiring
In older electrical panels and outdoor conduit runs, white insulation yellows and eventually turns light brown due to UV and thermal aging. Black insulation can fade to a dark, chalky grey. When the colour code in electronics and wiring becomes illegible, you must abandon visual identification entirely.
When dealing with faded mains wiring (>50V AC), treat every conductor as energized. Turn off the main breaker, apply a lockout/tagout device if applicable, and verify the circuit is dead using a Category III or IV rated digital multimeter. Test the meter on a known live source first (the "Live-Dead-Live" test) to ensure the meter's internal fuse hasn't blown, which could give a false "dead" reading on an energized wire.
If you are extending an old circuit with faded wires, use coloured heat shrink tubing or high-quality vinyl electrical tape (like 3M Super 33+) to re-identify the conductors at every termination point according to your current regional code. Never mix IEC and NEC colour palettes within the same junction box or enclosure; if an IEC-stamped appliance cord (Brown/Blue/Green-Yellow) is hardwired into a US NEC panel, clearly label the disconnect and use appropriate wire nuts to transition to local NM-B cable colours.
