If we often use red in software to warn someone to think before interacting with something, like a delete button for example, why do serious power tools like circular bench saws have big red buttons to cut the power in emergency situations?

images of circular bench saws

Surely you want the user to think as little as possible about what they are wanting to do before stopping a machine that might be causing serious injury or death.

Which of the above is getting it right? Or is there some fundamental difference between the two situations that means red in software makes people think about what they are to do but red in real life makes you react as quick as possible?

  • 2
    as a PS, the one with the foot placed kill switch demonstrates excellent design in a product
    – Toni Leigh
    Dec 1, 2013 at 9:38
  • Software interfaces and power tools are used in very different ways for very different purposes. I'm not sure there's a contradiction there. Just very different scenarios.
    – DA01
    Dec 2, 2013 at 1:19

4 Answers 4


Red doesn't always mean danger. It primarily is a signal color that attracts attention.

The emergency stop is red because it is to be used when the situation is dangerous and you need to find the thing quickly. Red fire alarms, red fire hoses, red whatevers all denote: "here I am" so they are identified and found quickly in an emergency.

Red is of course also used to spell "danger": red traffic lights, all road signs with a red border warn of danger (by forbidding things that would put you in that danger), ... And that's where your analogy comes from.

Even in software it isn't always a warning, however. Quite the opposite. Red is also used to signal errors. These are hardly dangers or emergencies. Merely stuff that needs to be corrected before the system will accept your request. And it is used on many websites for the call to action button simply because it attracts attention and the website owner wants you to find it quickly.

I would actually advise against using red for buttons that perform dangerous actions. Buttons performing dangerous actions should never be the default action (there are a couple of exceptions, search this site) and by analogy should not be red.

  • Red looks like a dark yellow for those with deuteranopia type color blindness. This is why designing to avoid one color as the only means of communication is important. The shape of a stop sign and the tiered-ordering of traffic lights are two examples. Dec 3, 2013 at 16:01

There is also a cultural aspect with colors, as an example - red does not mean danger in some eastern countries like china, where red symbolizes good fortune and joy...

In other countries, people read from right to left...

Both the cases in this question probably ignore it, and these cultural differences are way to often forgotten.

An infographic on colors in cultures: http://www.informationisbeautiful.net/visualizations/colours-in-cultures/


Color theory says that yellow catches the most attention. So they are both doing it wrong.

  • 1
    Possibly, but decades (if not centuries) of convention makes them red. And convention in it self has a lot of value that you only go against at your own peril. Something you don't want to do in emergency situations. Dec 1, 2013 at 13:43
  • Not really, you can find yellow buttons everywhere (see OP's link). Even firetrucks are becoming yellow. Dec 1, 2013 at 13:46
  • 1
    Really? Firetrucks? Wow. By the way, though I see some yellow kill switches emerging in OP's link, most uses of yellow are on the safety guards, not the kill switches. Not sure I would like the same color for the safety guards and the kill switch. It seems to detract from the kill switch's significance. If that is gonna be yellow, the safety guards should be another color, not sure what though. Dec 1, 2013 at 16:02
  • We'd need a citation for that statement
    – DA01
    Dec 2, 2013 at 1:20

They're really different worlds with different languages. Some significant differences between those 2 worlds is that software is much younger and much more complicated. Basically, software is in its infant stage, and even in its infant stage software UIs are much more complex than industrial UIs. (No doubt they'll get simpler but they won't get that simple.)

It is interesting to consider the evolution, more specifically the evolutionary sieve that these UIs have been through or are going through. Industrial UI fails can result in death or injury, while software fails are almost always less painful (I understand medical, military, and some other software applications have life/death implications but these applications have their own special rules and languages, they're specialized fields now and I'm setting them aside for the purposes of this answer/discussion).

The language of software UIs is rapidly evolving and hasn't come of age yet. The meaning of a red button hasn't come close to consensus in software UIs. And I doubt it will soon - it seemed like only last month the red button closed the window (on Mac).

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