If your industrial machinery has a "self-destruct and kill everyone" button, then I think the colour of it is the LEAST of your problems!

Seriously, though, too much color is distracting and you should NEVER use it as the sole way of indicating something 'mission critical' since different people perceive colour very differently.

Who says that only the color is the distinguishing feature?

And if you are thinking about colorblind people when mentioning color perception, then either let them rely on other aspects (ex: shape) or don't allow colorblind people to operate the machine. I know it is not very inclusive, but if colorblindness make it more likely for the operator to kill everyone, then it is for the best (I am mostly thinking about commercial airline pilots here).

And I don't find too much color distracting. Bad use of color is, but signage often use the whole rainbow with great success. For example, metro systems all over the world assign each line a dedicated color, making for quite colorful maps, and it works, that's why they all do it.

Not OP but guessing that this is about metaphorical self-destruct button (that has other important functions beside killing everyone).

Have you every been in airplane cockpit? There always is a switch that cuts enginees off and from what my pilot friend tells me using it in mid flight is more or less equal to killing everyone. And yes, as far as I remember it is big and red and have a lot of "do not touch" vibe around it.

The point is that it's distinguished by a lot more than just color. Shape, positioning, texture, etc are all used to seperate functionality (which is a hard-earned lesson in aircraft: there have been plenty of accidents because a pilot confused two similar levers/buttons/etc - one famous example was the lever to raise the landing gear being next to the throttle, which resulted in more than one case of it accidentally being raised while landing)

> There always is a switch that cuts enginees off and from what my pilot friend tells me using it in mid flight is more or less equal to killing everyone.

Now I'm curious about that! Is that for a situation in which there is absolutely no hope, but bringing the plane down *now* would be better than not doing so? I.e. it's a kind-of aerial trolley problem?

I actually did not ask when you should use this but I guess this could just be normal engine off switch that is always used when on ground (just you should never touch it mid air) or maybe something also usefull when when you have some fire-like situation going on. The whole not use when flying as far as I remember was because it can be really hard to get the engine to work again. And the look of the switch conveyed this message really well.

Yeah, we learned a lot about user interface design during WWII from things like this.

The B-17 was one of the first 4-engine planes and some people thought it was impossible to fly, but really there were issues because the "raise/lower landing gear" and the "dump fuel overboard" switches were basically next to each other and used identical toggles to save money.

Now the landing gear switch is a big handle with a wheel on the end aka it looks like a landing gear and the fuel dump switch is under a protective Molly cover and they are far apart.

With the cancel action, that's 4 :p