I'm working on a windows application that is showing the realtime status of a particular piece of equipment. While operating the equipment (via the application), two important values & labels are displayed in GREEN to denote safe/normal operations. And when they go above a predetermined level they get displayed in RED to denote an alarmed state.

Primary Voltage:    18 V

Motor Temperature:  100 C

I've been instructed to display flashing red text for the alarmed state, in order to draw the user's attention to the value. The option of popping up a message box alert has been ruled out. As has playing a sound, due to the noisy operating environment.

I can see the reasoning behind wanting to make it flash, but it just seems wrong somehow (flashback to the web of the late 90's). Does anyone have any better ideas? Would icons next to the label be appropriate?

NB: One advantage of flashing is that it aids those who are colour blind, who can't distinguish between green and red, but in this case the operators of the software are specifically required to not be colour blind.

NB 2: The two values being monitored (primary voltage and motor temperature) are not controlled by the software. Voltage is increased or decreased by the operator via a physical knob. The motor temperature is just a read-only sensor - if it reaches an alarmed state the motor would be shutdown by the operator via a physical motor on/off switch.

UPDATE: Thanks for your great answers. I have tried a few of the suggested solutions. The one I think worked best is the following:

  • Flashing the background instead of the text colour. The text colour remains static and is left as the default (black). Alarm OFF is shown as green background.
  • For Alarm ON, display a simple 'animated' colour cycle between red and white.
  • Animation cycle lasts 1 second
  • Animation uses a 'sawtooth' function:
    • at 0 sec show Red 100%
    • at 0.2 sec show Red 75% white 25%
    • at 0.4 sec show Red 50% white 50%
    • at 0.6 sec show Red 25% white 75%
    • at 0.8 sec show White 100%
    • repeat
  • 5
    If this is as critical as you say, you probably should consider implementing some kind of auto-shutdown after some reasonable time of the values exceeding the limits.
    – user
    Nov 22, 2011 at 9:35
  • 1
    to the left of the text: Normal: NO or green icon with checkmark; alarmed state: red icon with exclamation point Nov 22, 2011 at 15:02
  • @Michael the two values being monitored are not controlled by the software ... they are controlled by a physical knob for increasing/decreasing the voltage and an on/off switch for the motor. Nov 23, 2011 at 0:14
  • 1
    Ah, so this is sensor read-out only. I thought it was some kind of control system. Never mind the auto-shutdown, then.
    – user
    Nov 23, 2011 at 9:25

6 Answers 6


How about:

  • not making the text flash, but the background. This will improve readability of the text itself.
  • work with an "animation" so that the background does not flip on/off but gradually fades in and out.
  • 2
    Great idea regarding the control background colour, thanks. The animation idea I will consider as well. The only issue with animation for me is that in WPF (which this is written in), I've seen CPU usage spike badly when doing any sort of animation. Nov 22, 2011 at 7:26
  • 6
    Agreed, flash something else, but never hide the text (which is what flash/blink does 50% of the time). You want to draw attention, but also make it easy to read the error quickly. Nov 22, 2011 at 10:06
  • 3
    Isn't fade in / fade out animation too smooth for an alarm? I mean, a blinking element next to the text would do the trick I guess. Nov 22, 2011 at 11:38
  • 1
    Depends on how fast you fade in an out. I guess it's also a design issue. One of the concerns is not create something like a 90s website, like an animated gif of a rotating red light. Simply blinking looks amateurish imo. Nov 22, 2011 at 12:45
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    +1 pulsating lights are way underused in our lives ;) It's easier to make stuff flash/blink but pulsating stuff feels much more polished. Shouldn't it also be easier to detect as it's constantly changing instead of just changing when it flashes (like twice a second)? Perhaps pulsate the entire screen background, not too much so text becomes hard to read - but so the entire screen is easy to spot from a distance? Nov 22, 2011 at 15:31

It really depends on the nature of the equipment and the seriousness of the alert.

Does a high temperature mean that over ten years, this particular piece of equipment will fail to weigh out precisely 1.2 kilograms of potatoes, and instead perhaps will weigh out 1.21 kilograms of potatoes? In that case, I would say blinking red text is perhaps overkill.

Or does a high temperature mean that the nuclear reactor is about to melt down? In that case, by all means, make the text red and flashing.

In short, your instinct to avoid blinking text is well and good, but I can see some extreme cases where blinking, flashing and otherwise annoying techniques might be fully justified.

  • 2
    thanks for your comments - yes in this case it is quite serious as it's mining equipment containing electronics rated to a specific maximum temperature. A few minutes above the threshold could result in it being damaged. Nov 22, 2011 at 7:18
  • 2
    Flashing text is harder to read, though. I suggest flashing something else. (Bart suggests flashing the background, for example.)
    – Roy Tinker
    Nov 22, 2011 at 17:40

For accessibility reasons I propose to make the alarm state background dark red striped on a lighter red canvas.

Additionally have a warning icon which pulses.

This way even people with a color vision deficiency will notice that something is wrong because the background has diagonal stripes in another shade than the background and an icon that is pulsating.

  • +1 from me, I like the icon idea and is an approach I like to use for website validation. Nov 22, 2011 at 13:42

How frequently does the "alarmed state" occur? If it occurs too frequently, then the visual cues provided will fail to have the intended effect over time. If it is something that occurs but once on a fateful day, it would be difficult for the user to realize what exactly it implies and act accordingly in time.

I believe that if the "alarmed state" is extremely serious in nature, then everything ELSE in the display should be greyed out and a few lines of helpful hints on "what to do now" under the alert sign/ text should appear in normal font.

  • I agree, but doesn't that come very close to the already ruled out option of showing a popup message? Nov 22, 2011 at 12:46
  • 1
    Nice suggestion regarding greying out the other areas of the UI. I'm hoping that whatever flashing method I use will be sufficient to get the operator's attention, who is basically permanently watching the screen while operating the equipment. Nov 23, 2011 at 0:40

Flashing is appropriate: human perception is better in detecting changes and movement than static content (sometimes, quite large changes are overseen if the changes are interrupted with something else (change blindness).) Teaching the operators to scan their instruments helps overcome this, but changes and flashing are always getting much more attention.

As for the advice of changing the background: I would test this thoroughly before implementing. My suspicion (but I don't have resources to back this up - therefor test it) is that it would make the message harder to parse. The brain is processed to pay attention to changes, which would mean that the attention is drawn to the background, away from the text. I also don't think people have much difficulty parsing flashing texts - they occur quite frequently.


First consider how often you believe alarmed states to appear and how important the alarm is. It is important not to overload the user with flashing elements (unless there is something drastically wrong!). Also make sure you use them in the correct instance. If users always see the alarmed state and get used to ignoring it, then it fails to be of use (similar to over use of modal dialogues)

Maybe you could flash an icon and not the text? Or grow/contract the icon in someway? Make sure you use a consistent position for any icons so the user knows where to look.

I would have concern about the readability of flashing the text itself.

Also do you need to consider accessibility, I assume not so much as you mention the users need to have good colour vision etc. But be aware that "flashing" may not be conveyed to assistive technologies.

  • 1
    Nice suggestion regarding a growing/contracting icon. In this app there is only these specific two values that are important enough to 'flash', so at least there shouldn't be any chance of the user being overloaded. Nov 23, 2011 at 0:57

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