Buying guide
Push Buttons, Selector Switches and Indicator Lamps: Colour Codes, Contact Types and Ratings
The push button colour code on industrial machines is based on IEC 60204-1 and IEC 60073: red for emergency stop; white (preferred), green, grey or black for start; black (preferred), grey, white or red for stop; yellow for an abnormal condition; and blue for a mandatory action such as reset. Indicator lamps use the same colours with their own meanings. This guide gives the full table, then the choices that decide whether a control station works and lasts: size, contacts, emergency stop, ratings, lamp voltage and IP protection.
The short answer
Colour tells an operator what a control does, so use it consistently. The table shows the meanings commonly applied under IEC 60204-1 (electrical equipment of machines) and IEC 60073 (coding of indicators and actuators).
| Colour | Push button | Indicator lamp |
|---|---|---|
| Red | Emergency stop (red mushroom, usually on a yellow background). Permitted for stop or off, but not recommended near an emergency stop. | Danger, or an emergency needing immediate action. |
| Yellow | Intervention in an abnormal condition, such as suppressing it or restarting an interrupted cycle. | Abnormal condition, or a critical state approaching. |
| Green | Start or on; widely used. | Normal or safe condition. |
| Blue | Mandatory action, such as reset. | Condition needing operator action (mandatory). |
| White | No specific meaning; the preferred colour for start or on, also allowed for stop or off. | Neutral or general information. |
| Grey or black | No specific meaning; allowed for start or on, and black is the preferred colour for stop or off. | Not normally used for lamps. |
Treat this as common practice, not a quotation: the standards allow several colours for start and stop. IEC 60204-1 prefers white for start and black for stop. It also allows green, grey or black for start and grey, white or red for stop, but recommends against red for an ordinary stop near an emergency stop. Follow your machine standard and the client specification.
Size and actuator types
The industrial standard for push buttons and indicators is the 22 mm control station, which needs a round panel hole of about 22.5 mm. 16 mm devices suit compact panels and 30 mm devices appear on some older or imported machines; neither is interchangeable with 22 mm, so measure the hole first.
| Actuator | Where it is used |
|---|---|
| Flush | Often used for start buttons. Level with the bezel, so accidental presses are less likely. |
| Extended | Often used for stop buttons. Stands proud: easy to find with a gloved hand, easier to knock. |
| Mushroom head | A large target for the palm, and the head shape used for emergency stop. |
| Illuminated | Shows status, for example lit while the motor runs. |
| Double-headed | Start and stop in one hole, typically green “I” and red “O”, usually with one NO and one NC contact. |
| Selector, 2 or 3 position | Mode choice, such as manual/auto, local/remote or hand-off-auto. Maintained or spring-return. |
| Key selector | Mode or access control; the key often comes out in only some positions. |
| Pull or twist-release emergency stop | Latches when pushed; released by pulling or turning. |
A control-station selector switches control circuits only. To switch a motor, use a cam switch or starter rated for the load; to isolate a supply, use a switch-disconnector marked as suitable for isolation; see switches.
Momentary or maintained, and why stop buttons are NC
A momentary (spring-return) button changes its contacts only while pressed: use it for start, stop, jog and reset. A maintained (latching) button or selector stays where it is left: use it for modes and emergency stop. For motor control, a momentary start button with a holding (seal-in) contact on the contactor keeps the motor off when power returns after load-shedding; a maintained switch wired straight to the coil would restart it unexpectedly.
A normally open (NO) contact closes when pressed; a normally closed (NC) contact opens. Start buttons use NO and stop buttons use NC for a fail-safe reason: a broken wire or loose terminal opens an NC stop circuit, so the machine stops or cannot start. On a NO stop button the same fault changes nothing you can see, and the stop fails when it is needed. Wire the stop in series with the coil and the start in parallel with the holding contact.
Emergency stop devices
An emergency stop is a specific device, not just a red button. IEC 60204-1 requires a red actuator and, where there is a background around it, a yellow one, and IEC 60947-5-5 covers electrical emergency stop devices with mechanical latching. Look for:
- Red mushroom head with a yellow legend plate or surround, within easy reach.
- Latching: it stays pressed until released on purpose, by turning, pulling or a key.
- Positive-opening (direct-opening) NC contacts: the actuator forces the contacts apart through rigid parts, not only a spring.
- No automatic restart: releasing it must not start the machine; a separate start command is needed.
An emergency stop does not make a machine safe by itself. A qualified engineer decides the stop category and the safety circuit, including any safety relay, from the machine’s risk assessment.
Contact ratings, control voltage and lamps
IEC 60947-5-1 rates control circuit contacts by utilisation category, so do not size a block by the single current figure on it. AC-15 covers switching electromagnetic loads on AC, such as contactor coils, relays and solenoids; DC-13 is the DC equivalent. Compare the rating at your control voltage with the coil data. DC ratings are usually lower than AC ratings, because a DC arc is harder to extinguish. Never use these contacts to switch a motor or heater directly. The relay vs contactor vs SSR guide explains these categories in more detail.
Typical control voltages are 24 V DC (common where a PLC is used; see how to size a 24 V DC power supply), 24 V AC, 110 V AC and 230 V AC. A lower voltage is generally safer to touch. Every block, lamp, relay and coil on the circuit must be rated for it.
LED lamps are now the usual choice: low current, cool running and long-lived, while filament lamps run hot and burn out. The lamp voltage must match the control supply. A 230 V lamp on a 24 V circuit stays dark or barely glows, and a 24 V lamp on 230 V can be destroyed within moments. Check whether the lamp is rated for AC, DC or both.
Protection, mounting and maintenance
- IP65 – dust-tight and protected against water jets.
- IP66 – dust-tight and protected against powerful water jets.
- IP67 – dust-tight and protected against temporary immersion.
Start with IP65 for dusty areas such as workshops, IP66 where the station is hosed down and IP67 only where temporary immersion is possible, and follow the site specification. The rating covers the front of the device, fitted with its gasket in a clean, flat hole; the rear is often only IP20 (finger-safe), so the enclosure behind it (see distribution panels) and the cable glands must do the rest.
Plastic bezels do not corrode and suit most indoor panels; metal bezels, chrome-plated or stainless, resist knocks and heavy cleaning. A rubber boot helps against dust and splashes; a missing gasket or torn boot weakens the protection. Ordinary push buttons are unsuitable in classified hazardous areas, including where flammable gas or combustible dust may be present; those need Ex-certified devices whatever the IP rating.
Check the depth behind the panel, because contact blocks stack behind the actuator and wires need room to bend. Follow the maker’s spacing, and add a legend (START and STOP, “I” and “O”, or text in your operators’ language) so colour is never the only clue.
Contact blocks wear, especially near their rating. They usually latch onto the back of the actuator, so a worn block can be replaced without drilling the panel. Isolate and prove the panel dead, note the wiring, replace like for like and test every function.
How to choose: an 8-step checklist
- Function and colour – chosen to your machine standard and client specification.
- Size – 22 mm unless the existing panel hole says otherwise.
- Actuator – flush, extended, mushroom, illuminated, selector or key; momentary or maintained.
- Contacts – NO for start, NC for stop, with enough blocks.
- Emergency stop – red mushroom with a yellow surround, latching, positive-opening NC contacts.
- Contact rating – AC-15 or DC-13 at your control voltage.
- Voltage and lamps – 24 V DC, 24 V AC, 110 V AC or 230 V AC, with matching lamps.
- Protection and fit – IP rating, bezel material, depth, spacing and legends.
Browse push buttons and indicators, switches, contactors and motor starters and distribution panels, or start from a brand such as Schneider Electric or Siemens. Send a photo of the old device’s label on WhatsApp and we will help you match it.
Frequently Asked Questions
What colour should a start button and a stop button be?
Green start and red stop are common, but IEC 60204-1 prefers white for start and black for stop, and advises against red for an ordinary stop near an emergency stop. Grey is allowed for both. Yellow is for intervention in an abnormal condition and blue for a mandatory action such as reset. Follow your machine standard and the client’s specification.
Why is a stop button wired as normally closed?
A normally closed stop contact is closed while the machine runs, so a broken wire, a loose terminal or a failed contact opens the circuit and stops the machine or prevents a start. This is fail-safe behaviour. A normally open stop button would do nothing if its wire broke, and the fault would stay hidden until someone pressed it in an emergency.
What is the standard push button size and panel hole?
The industrial standard is 22 mm, which needs a round hole of about 22.5 mm in the panel. Smaller 16 mm and larger 30 mm devices also exist, but they are not interchangeable with 22 mm. Measure the hole in the panel or the old device before ordering, and check the maker’s cut-out drawing for the exact size and the panel thickness range.
What makes an emergency stop different from a red stop button?
An emergency stop device has a red mushroom-head actuator, usually on a yellow background, that latches when pressed and needs a deliberate action to release, such as turning, pulling or a key. Its normally closed contacts are positive-opening (IEC 60947-5-5). A plain red stop button is not built to do this. Emergency stops belong in a safety circuit designed from a risk assessment.
Can I use a 230 V indicator lamp on a 24 V control circuit?
No. A lamp rated for 230 V will stay dark or glow faintly on 24 V, and a 24 V lamp on a 230 V supply can burn out at once. Check the voltage marked on the lamp or LED module, and whether it is rated for AC, DC or both. Some LED modules accept a wide voltage range, but only if their datasheet says so.
Which IP rating should a push button have in a dusty or washdown area?
IP65 is a common choice for dusty areas such as workshops, IP66 where the station is hosed down, and IP67 only where temporary immersion is possible. The rating applies to the front of the device when it is fitted correctly with its gasket, and the enclosure and cable glands behind it must be suitable too. Follow the site specification.