Indicator Light Color Standards


Thread Starter

Brian Kukulski

Are there any standards (API,CSA,UL,ISO etc) or
recommendations as to what color light(s) should be used to indicate the status of valves, motors or pumps?

One philosophy is: Red = ON/OPEN; Green = OFF/CLOSED The other is opposite. Which is more correct and by what standard?

Brian Kukulski
e-mail:[email protected]

john coppini

by far the most used convention is green=on/running; red=off/halted; yellow=transitional/starting mode. problem is: a stop command requires a mouse click on a green icon, but this hasn't been a problem in my experience. alternative is to provide an icon showing with pilot lights where green=on, red=off, and a red (to stop) or a green (to start) "push" button.

but on the other hand, live dangerously! the hell with convention! splitting hairs is never fun...try chasing women! wine, women, and song....yee haaaaa!

Ron Gabaree - Vitronics Soltec, NH.USA

It is my experience that different industries have different standards of pilot light color standards:

The Machine Tool Builders (and others) use 'Green' for Start,Running, or On...

The Power Generation Industry, especially where combustion takes place, 'Red' indicates On, Hot, Fire, Combustion.... and 'Green' indicates Cold, Off, Safe,....etc

The Process Industries...Pulp & Paper Wastewater Treatment, Food Processing, etc are split on the usage of Red/Green...and it is done both ways, but usually only 'One Way' within a facility or organization.

Best Regards,
Ron Gabaree
Technical Services
Vitronics Soltec
2 Marin Way
Stratham, NH 03885
603-772-0210 ext 223

Please do not live dangerously, as previously suggested. I recommend that you use the NFPA 79 Electrical Standard for Industrial Machinery. I have the 1997 Edition, which clearly states what colors are used for what in Section 13.1, Table 8. The table is a little too large to put in this message.

Here is an URL for the NFPA Current Codes. Just click on NFPA 79.

Hope this helps!

Gerry Moore

Warren Postma

We had always been using Green as "Good/on" and Red as "Bad/off".

Then much to my surprise I found out that in the Electrical Utility Industry they use the opposite convention to my "traffic light" mentality. Ie: Red means "on", because a wire or bus is "hot" or "dangerous" when current is flowing on it, and green when it is "cold" or "safe", therefore Off. I still find this insanely confusing.

A "modest proposal": I suggest we cease using Red, Yellow and Green, and begin to use Chartreuse, Taupe, and Cerulean instead in all electrical engineering applications, as they have fewer sets of pre-conceived associations. After spending a whole day dealing with conflicting neural associations between the meaning of little blinking red and green lights, I might accidentally run a red light while driving home.. It makes sense right? Red means current is flowing, and when in rush hour traffic I feel a
lot like I'm just one electron among so many. Well, you get the idea?


Warren Postma
ZTR Control Systems

Brian Browder - Hatch Associates Consult

I would never make a decision myself about lamps on a control station (i.e. illuminated pushbuttons). The user or the industry will have strong preferences for good reasons, as pointed out in the second response. I would always simply ask operations management, presenting any standards or arguments I had for the situation. You may find yourself using red at some stations and green at others for the same condition, for very different reasons.

HMI design, on the other hand, calls for simple, uniform answers. That's where the designer's ideas are more likely to be accepted.

The best argument I've heard is that HMI screens are (should be) cluttered, so normal/abnormal states should be simple and visually obvious.

The background and process illustrations should be neutral (greys, browns, or muted colors). When all is normal a screen should be full of a calm green (controllable elements only).
Warnings (i.e. not normal but acceptible, like PID-controller-in-manual) should appear as bright yellow.
Abnormal, alarm, and fault conditions should appear as bright red, flashing until acknowledged.
In addition, default coloring should be something otherwise meaningless, like magenta, to indicate a communication failure.

As the first response pointed out, you can deal with the inherent confusion in layers. The animated control element can follow one standard, while a box that pops up to control that element can show all details and colors like a pushbutton station. That gets complicated, and is more a matter of negotiation than reason.
There is a U.S. standard for industrial machinery, National Fire Protection Association(NFPA) 79 "Electrical Standard for Industrial
Machinery" which has color codes for push buttons, illuminated push buttons, and pilot lights. This is from the same people who publish the National Electrical Code(NEC) - NFPA 70.

Bill Mostia

William(Bill) L. Mostia, Jr. PE
Principal Engineer
WLM Engineering Co
Independent I&E Consultant
P.O. Box 1129
Kemah, TX 77565 USA
E-Mail: [email protected]

These opinions are my own and are offered on the basis of Caveat

Dave Ferguson

As I replied earlier, I beleive it is SP5.5 ISA standard defines this. Look at their site at They have very detailed standards
for this. i am not sure that they are the best for all situations but they are a standard.

Dave Ferguson

Brady A. Johnson

I worked for one company that used red and green to indicate on or off, but I always had a hard time explaining to others which one was which because I could never remember!

Of late I have taken to using red to mean "on" and gray (dark or unlit) to mean "off". I like to think of it as looking at a single-color LED that is on or off. This seems to make displays
fairly obvious for things like "the door is open," "the pump is running," "the alarm is activated," etc.

Brady A. Johnson
[email protected]
I think the best answer is to ask someone you know who IS NOT AN ENGINEER and see what makes sense to them. I use the green=on philosophy in my plant and have never had a question as to what green means.

Darin Jett


> Then much to my surprise I found out that in the Electrical
> Utility Industry
> they use the opposite convention to my "traffic light"
> mentality. Ie: Red
> means "on", because a wire or bus is "hot" or "dangerous"
> when current is
> flowing on it, and green when it is "cold" or "safe",
> therefore Off. I
> still find this insanely confusing.

In our utility we use the opposite - i.e. for a switch or breaker, Green=closed, Red=Open (and two bit devices add Yellow=Travel, Magenta=Invalid). At least we are consistent with ourselves :)

Robert Antonishen, P.Eng.
Sr. Eng - IMO Integration Project
Commercial Systems - Commercial Operations
Ontario Power Generation
phone 416-592-1510 fax 416-592-2889
[email protected]
This only issue that is standard to the control on any device is that "Red" indicates a failure or some type. "Green" is for run, or on.

Other than that it is as applied by common understanding. My company also has Amber colors for use on different applications. Right now i am trying to find a 1/2 220v Blue indicator light.

Hope this helps.