HMI Screen Graphic Colours - British Standards?


Not sure if i’m posting in the correct section here.

Anyway, I have a query in relation to HMI screen graphics colours used by Vendors. Most of them are using RED stop / alarm and GREEN open / run. This is the approach taken by most vendors as a standard and what would be expected. However with one vendor, they are actually using the opposite standard for the Graphics.

Is there a British or EU Standard that list the correct graphic colours??


The origins of this convention dates back to the railroad signaling practices of 1830s. The first road use was in Dec, 1868 in London. However, red, as the color of blood, was used as a danger signal by the Roman legions, as they bore red banners into battle 2,000 years ago.

The interpretation of red, yellow, and green for status is consistent globally due to the UNESCO Vienna Convention on Road Signs and Signals (
). Chapter III, Traffic Light Signals Article 23 (Signals for vehicular traffic) defines the worldwide convention for traffic lights.

There is a Microsoft convention dealing with this issue that references the above (

With respect to CFR 21 regulations, I don’t believe there anything specific regarding colors. However, I am aware of issue with an infusion pump where the start and stop buttons were located too close together. This issue let to a global recall and re-design of the input device.

Finally, from a safety perspective, this is beyond words. Depending on what the system does, the only thing I can think of is res ipsa.

ok, thanks for that reply

Very well put RTMcFadden!!

There is a book “The High Performance HMI Handbook” that can be very helpful to you. The short answer to your question is: “Red and Green are both wrong to use regardless of which one means Stopped or Running.”

A High Performance HMI has grey backgrounds. Why grey? Because it is an industry best practice for control rooms to be well lit (slightly brighter than a regular office lighting). Well lit control rooms encourage operator alertness. Now, if the control room is well lit, a background color that minimizes glare is needed. A light grey does the trick. As it turns out, light grey is a great color to have as background because bright colors (such as red/green) can be used to attract the operators attention. It is a best practice in industry nowadays to use these bright colors to attract attention to the ABNORMAL ONLY (such as an alarm). If you have 2 pumps and one of them is a spare, why use bright colors for something that is completely normal. The best practice is to show the pump that is stopped in darker grey than background, and the one running lighter grey than background.

In short, High Performance HMIs should look dull if everything is normal. Bright colors AND ANIMATION is reserved for abnormal situations that should get the operators attention. DO NOT RELY on vendors samples for your HMI design. Their examples are some of the worse HMIs in industry. Read the book. There is a whole lot more about HMIs. I’ll be pleased to elaborate more if you need me to.

Happy HMIs.