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Green,red lights

Green,red lights

Green,red lights


I do have a question:

There is a standard (USA and/or Europe) about the color  of the illuminated pushbutton?. e.g.: green light shows the status of the machine (running) or the pushbutton action : start?

This applies also at the HMI's buttons.

Thank you

RE: Green,red lights

As far as I am aware, there is no U.S. standard for light colors.  Even different facilities in the same industry do it differently.  Sometimes green is ON, red is OFF, and sometimes just the opposite.  It is almost always one or the other, (you never see BLUE used for ON).  

In the electric utility industry, RED is nearly always used for ENERGIZED, ON, etc.  Valves are shown RED for OPEN at most power plants that I have been in.   

In other industries, it's a dog's breakfast - a little of everything.  

My sense is that MOST facilities use RED for ON, but there are a lot that use GREEN.  

You have to ask every time.

RE: Green,red lights

Thank you dpc. It is my impression too. Just makeing it sure.


RE: Green,red lights

There is only a guide, which is one of the many human factors handbooks such as MIL-HDBK-1472.  

The reason there is no standard is that there is no agreement on what colors and so forth should mean, particularly when there are two equally valid viewpoints.

As an example, while typical usage implies that red means stop and green means go, my portable hard drive has a steady red when it's idling, and green when it's been accessed.  From the perspective of the drive, that seems reasonable, but from the user's perspective, that's backwards, because when it's red is the time when I could potentially disconnect it, while when it's green is when the disk is being accessed and is definitely not the time to disconnect.

Your best bet is to mock up your application and try to use the colors and indicators against your usage of the hardware.


RE: Green,red lights

Surely it’s not a trivial issue and has plently of arguments for both approaches.  As a starting point, maybe it would be reasonable that one influence could be that red lamps indicate a condition of operation yielding some hazard, like a printing press or hydraulic pump, versus green indicators annunciate a process that minimizes a hazard, like maybe a spray-booth or baghouse exhaust fan.  Certainly within a facility and a particular industry consistency is usually warranted.  

RE: Green,red lights

hi all
 busbar how right you are yes it's a mish mash but it's generally agreed that unless there is an underlying philosphy (spelt how?) like the power generations view of red = hot or danger then green and red match the traffic  light senario. make it green to get going and red to stop it.
 the default colour for an Estop pushbutton is red and you've gotta order otherwise.
I believe from memory petro chem is pretty standardised on red for stop it, it's stopped, alarm or danger.
green for start it, its going or it's safe.
yellow for alert, be advised or concern.
blue for attention here or giving data
Or that's the way we structured a lot of control panels and screen graphics over the years.

Does anyone work for the likes of Honeywell, Foxboro, yokogowa et al. These guys used to publish bulletins on this sort of things and maybe some one can put a pointer to some on-line data

Best to all & merry x mas

RE: Green,red lights

hi all,

Thank you for the suggestions.
There is no problem for individual pilot lights (status = red/green (is) stopped/running) or simple push buttons (action = red/green (you can)stop/start ). The problem is  when you put them toghether because of their almost opposite meaning- if it is stopped ,you can start it.
My problem is ,also, the HMI- where i change the colors on the buttons.
I have  buttons to start and stop the devices. Only one for each one.
I choose the color for the HMI buttons to reflect the status of the devices.


RE: Green,red lights

In addition to MIL-HDBK-1472, there are a number of military standards for "knobology", which might be overkill for your application.  In those standards, there are recommendations for altering the shapes and positioning as well as the color to distinguish between otherwise physically, but not functionally, identical controls.


RE: Green,red lights

IRstuff Where i can find MIL-HDBK-1472?


RE: Green,red lights

In the absence of a defininitive standard, it may be worthwhile to talk to the folks who will be operating the system to see what they expect or what is most widely used in the plant where the system will be located.  You want the controls to be as intuitive as possible and not every person sees red as a hazard color or green as a safe color.

When life gives you lemons, make lemonade.  When life gives you grenades, well....

RE: Green,red lights

I like to point out that there is a standard. It is too often ignored. The standard is NFPA 79 "Electrical Standard for Industrial Machinery". Section 13 "Operator's control stations and equipment" covers this issue. The section has a Table 8 "Color coding for pushbuttons, indicator (pilot) lights, and illuminated pushbuttons. It is too long to detail here.
Europe has a similar standard EN 60204-1 "Safety of machinery-Electrical equipment of machines." Section 10 "Operator interfaces and machine mounted control devices" covers the issue.
Standards often do exist.....but just try getting people to follow them.

David Baird
Sr Controls Engineer

EET degree.

Journeyman Electrician.

RE: Green,red lights

Yes, NFPA 79 Sec 10 does cover this, if the pushbutton and HMI are used by an industrial machine, and if your AHJ has adopted this standard and is enforcing it.  The DOE (at least to my knowledge) has not adopted this standard so in my case I follow the home-brewed standard that our subject matter experts came up with after researching and debating the available standards and recommendation.  If wherever you work does not have a standard then you will have to make those decisions as best you can given the peculiars of your situation.

When life gives you lemons, make lemonade.  When life gives you grenades, well....

RE: Green,red lights

I dont know of any standard, Ill look into the one David mentions above. For  push buttons and opperator devices, ussually each customer we have (IP,LP,Roseburg-Forest,Carter-holt ETC) have a standard for all their plants, but they are not the same as each other.

Even Emergency stop, which is always RED light, some companies want the light ON when Estop is pushed, some want it OFF.

For HMI there are a few loose standards, more European and not followed by many people.

RE: Green,red lights

dwayned (electrical)

There is another European Norm Standard that specifies the Safety of Machinery - Indication, marking and actuation. Part 1. Requirements for visual, auditory and tactile signals. BS EN 61310-1:1995 IEC 1310-1:1995. Under this standard RED indicates DANGER // Prohibition in regards to safety of persons it indicats and Emergency as to the condition of the machinery or process.  GREEN indicates SAFE in regards to the Safety of persons and NORMAL as to the condition of machinery or process.



RE: Green,red lights

Not to confuse an already confusing issue, but what do people that are red/green color-blind to do?  I don't expect us to design around the minority that are color blind, just wanted to throw that into the mix.

RE: Green,red lights

They become very, very careful and they look for additional clues of simply learn them in real-time.  Even totally color-blind people can tell gray shade differences on any given comparison of red/green lights.


RE: Green,red lights

Twice in the last month or so I've heard of vendors using blinking lights rather than colored lights for the exact reason of color blindness.  Continuous = on, Blinking = stopped or something like that.  Haven't yet seen it installed.

My opinion is that this is mostly just a third option now available to confuse people even more.

RE: Green,red lights

hi all
 though technically colour blind to green and blue I have never managed to mix up the stop start or green and red yet. But don't ask me to land a plane on the small approach high /low indicators they fit at the end of the strip. They are useless untill i'm less than 2km out.
A suggestion for all here.It is not good engineering (or  manufacturing) practice to just fit a lamp or button. You would normally be expected to put a clear and intelligable label on it and those who are familiar with the machine/plant will use the light for a quick visual check.
I hope that doesn't sound too pompous it's not meant to be.

Merry xmas to all

RE: Green,red lights

There are a lot of standards addressing this issue of red and green pilot lights and push buttons: for switchgear IEEE/ANSI C37.11, Section 4.2, diagrams 1 to 8., For motor controls Nema ECS2-216.66., for other electrical equipment NEMA ICS-2, the old standard which is used in NFPA 79 is from 1967 JIC standard. Mil-Std-1472 contradict the other standards for red and green, I don't know what Europe uses.

RE: Green,red lights

I think we should drop this indicator color issue, as stated in several of the replys a "base" level standard does exist both in NFPA79 and EN60204. Common sense should be resorted to if these standards do not cover your needs fully. The question has been answered several times in the replys but it seems no one wants to follow standards and would prefer come up with their own alternatives.

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