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What do the colours of machine indicator lights and push-buttons mean?
Short answer
On industrial machines built to IEC 60204-1, a red indicator signals an emergency or hazardous condition needing immediate action, yellow (amber) an abnormal condition that needs intervention, green a normal state, and blue that the operator must do something, such as a reset; white is the neutral colour, used to confirm a command or where no other colour obviously applies. Red is also the colour of the emergency-stop actuator. The scheme is about machine state, so it reuses familiar colours for a different purpose than traffic lights; IEC 60073 is the IEC's general publication on coding indicators and actuators.
At a glance
Machine electrics
IEC 60204-1:2016 with Amendment 1 (2021)
Coding principles
IEC 60073:2002
Status colours
Red emergency · yellow abnormal · green normal · blue mandatory action · white neutral
Emergency stop
Red actuator on a yellow background (red also required by US OSHA)
The 2 standards
IEC 60204-1: Safety of machinery — Electrical equipment of machines — Part 1: General requirements
Issued by
IEC
Edition
2016, with Amendment 1 (2021) (2016)
Status
Current
Applies to
International; harmonised in Europe as EN 60204-1
Includes the colour rules for machine push-buttons, indicator lights and indicating towers.
Colour meanings in IEC 60204-1
Colour
Meaning
Paired with
Red
Emergency or hazardous condition needing immediate action; emergency-stop actuators (on a yellow background)
—
Yellow (amber)
Abnormal condition needing intervention
—
Green
Normal state
—
Blue
Mandatory action from the operator, such as a reset
—
White
Neutral: confirms a command or state, and serves where no other colour obviously applies
—
Status checked 1 October 2026. Summary only. The standard is sold by the IEC and national bodies; its tables and wording are copyright and are not reproduced. Consult the current edition and any national deviations. The meanings are as summarised for the 2016 edition in the DGUV test institute's checklist of June 2020; Amendment 1 (2021) was not read.
IEC 60073: Basic and safety principles for man-machine interface, marking and identification — Coding principles for indicators and actuators
Issued by
IEC
Edition
2002 (2002)
Status
Current
Applies to
International
The IEC's basic safety publication for indicators and actuators: general rules for assigning particular meanings to visual, acoustic and tactile indications.
Colour meanings in IEC 60073
Colour
Meaning
Paired with
Colour as one coding means among several
This record gives no colour table for IEC 60073, because none could be checked against the IEC or an official summary; the machine colours on this page are those of IEC 60204-1
—
Status checked 1 October 2026. Summary only. The standard is sold by the IEC and national bodies; its tables and wording are copyright and are not reproduced. Consult the current edition and any national deviations. The IEC catalogue shows a stability date of 2026 for this edition, so a revision may follow.
Summarised in Colourwise’s own words; not the text of any standard and not compliance advice. Always work from the current edition obtained from the issuing body.
State, not command
Machine colour coding answers 'what state is the process in, and does someone need to act?' Red means an emergency or a hazardous condition that needs immediate action; yellow means an abnormal condition in which someone needs to intervene, the kind of state that precedes a fault; green means the normal state. Blue is the odd one out: it does not describe a hazard level but tells the operator that a specific action is mandatory, a reset being the standard example. White carries no meaning of its own: it confirms that a command or state has been registered, and it is the colour for illuminated push-buttons to which no other colour obviously applies. Indicating towers, the stack lights on production lines, apply the same palette vertically so a supervisor can read a whole hall at a glance.
Why green is not always 'go'
People carry the traffic-light association into control panels, and that is sometimes dangerous. On a machine, a green lamp reports that whatever it monitors is in its normal, safe condition; it does not certify that the whole machine is safe to reach into, and a machine can be running normally and still be lethal. Push-buttons follow their own rules. Start or on buttons should be white, grey, black or green and never red; stop or off buttons should be black, grey, white or red and never green; yellow is for intervening in an abnormal condition and blue for a mandatory action such as reset. Because white, grey and black can serve for both start and stop, the standard expects such buttons to be told apart by structure, shape or position, so the colour is never the only signal.
Order matters on a stack light. IEC 60204-1 sets the colours of an indicating tower from the top down as red, yellow, blue, green and white, so position repeats what the colour says.
Emergency stop: the one colour everyone agrees on
Emergency-stop actuators are red on both sides of the Atlantic. IEC 60204-1 calls for a red actuator on a yellow background, typically a push-button made to be struck with the palm or fist, and keeps it red whether or not it is lit; US OSHA's colour rule requires red for emergency stop bars, buttons and switches on hazardous machines. The shared convention exists because an emergency stop is the one control an untrained bystander may need to find and use. The IEC standard does allow red for an ordinary stop button, alongside black, grey and white, but a designer who takes that option makes the real emergency stop harder to find in a hurry, and red is better kept off reset and routine functions altogether.
Designing panels people can read
Red, yellow and green are the three colours most affected by the commonest colour-vision deficiencies, and indicator lamps are small, bright and often seen against a dark panel. LED indicators can also look very different from the incandescent lamps the scheme grew up with: a narrow-band amber LED and a red LED can be closer in appearance than their filament predecessors. Good practice therefore pairs colour with position (a consistent order in stack lights), text or symbols on buttons, and distinct lamp shapes. Nothing on this page replaces the standards or a machinery risk assessment.
The data
Machine indicator colours and what they ask of the operator
Colour
Machine state
Typical operator response
Red
Emergency or hazardous condition
Act immediately; follow the emergency procedure
Yellow / amber
Abnormal condition
Intervene before it becomes a fault
Green
Normal state
None required — which does not mean safe to reach in
Blue
Mandatory action, such as reset
Carry out the specific requested action
White
Neutral: a command or state is confirmed
See the machine's documentation
Source: List for the safety testing of machines — Electrical equipment (test checklist against IEC 60204-1:2016, June 2020); International Electrotechnical Commission (IEC) webstore and catalogue. Indicator colours of IEC 60204-1:2016 as summarised in the DGUV test institute's checklist; the operator responses are Colourwise's plain-language gloss. The standard and the machine's own documentation govern.
What goes wrong, and what to do
Operators ignore a permanently lit yellow lamp
Why: A condition that is always 'abnormal' teaches people that yellow means nothing.
Fix: Fix the underlying condition or reassign the lamp; reserve yellow for states that need attention.
Red and amber LEDs look alike on a new panel
Why: Narrow-band LEDs close in wavelength can be hard to separate, especially for people with colour-vision deficiency.
Fix: Choose indicator LEDs with clearly separated colours, and add position or text cues.
How to check it yourself
Find the machine's documentation to see what each indicator colour is defined to mean.
Check that the emergency stop is a red actuator on a yellow background and that no start function is red.
View the panel through a colour-vision-deficiency simulation to see which lamps rely on colour alone.
What the evidence says
Each statement is labelled by kind — established fact, a standard’s requirement, observed market data, a convention, or Colourwise’s own interpretation or analysis — with the strength of the evidence behind it.
FactStrong evidence
IEC 60204-1, the general standard for the electrical equipment of machines, is current in its 2016 edition with Amendment 1 of 2021, and IEC 60073 on coding principles for indicators and actuators is current in its 2002 edition.
IEC 60204-1:2016 uses red indicator lights for an emergency or hazardous condition needing immediate action, yellow for an abnormal condition needing intervention, green for a normal, safe condition and blue for a mandatory action such as a reset, with white for confirmation and for illuminated push-buttons to which no other colour obviously applies.
Caveat: Taken from the clause-by-clause test checklist for IEC 60204-1:2016 published in June 2020 by the test institute of Germany's statutory accident insurers, not from the purchased standard. Amendment 1 (2021) and IEC 60073 were not read.
Under IEC 60204-1:2016 the emergency-stop actuator is red on a yellow background; start or on actuators should be white, grey, black or green and not red, stop or off actuators black, grey, white or red and not green; and indicating towers carry their colours from the top down in the order red, yellow, blue, green, white.
Caveat: From the same 2020 test checklist, which marks the start and stop colours as recommendations. The standard itself and its 2021 amendment were not read.
Using red for routine stop or reset controls as well as the emergency stop weakens the emergency stop's visual distinctiveness on a panel.
Based on: Follows from the purpose of reserving a single salient colour for the emergency function, as expressed in the IEC 60204-1 colour rules summarised by the cited test checklist and in OSHA's colour rule. IEC 60204-1 itself permits red for an ordinary stop actuator.
Related questions
Why is blue used on machine indicators?
Blue marks a mandatory operator action, echoing the blue of mandatory safety signs. It tells the operator that something specific must be done, rather than describing a hazard level.
Does a green indicator mean a machine is safe to touch?
No. Green means the process is in its normal state. A machine running normally can still be dangerous; safe access depends on isolation procedures, not indicator colour.
What colour should a stack light's top segment be?
Red. IEC 60204-1 sets the order from the top down as red, yellow, blue, green and white, so position reinforces colour. What each segment means on a particular machine should still be taken from its documentation.
Reviewed 1 October 2026. Colourwise summarises its sources in its own words and does not reproduce standards text or proprietary colour data. Spotted an error? Tell us.