I am working on an application that has a GUI-based control panel window that can be switched between several similar devices. Many typical use cases have users walk up to the panel, select the specific device they are interested in, glance at some key status information, initiate some simple commands, and leave. One type of error that occurs is that our users either think the screen is already configured to control the device they are interested in, or they (accidentally) select a different device and then proceed to initiate their commands (to the wrong device). We would like to reduce the occurrence of such errors.

What types of visual cues for a GUI screen that can be used to control different devices that can effectively aid users to quickly recognize that the device they think they are controlling is the one actually being controlled?

The control panel is about 900x600 pixels in a 1280x1024 screen. Real estate on this panel is somewhat limited. The indicator that selects / indicates the connected device is currently in the upper-left corner, and about 80 pixels wide and 20 pixels high.

Note -- One cue we have tried is to have the device number watermarked into the background of the panel. This has helped a somewhat. I am currently experimenting with background colors. We have up to 8 devices that share a control panel, so the colors need to be different enough that they are readily distinguishable, and certain colors (red, orange and yellow) are off limits, as area all "bright" colors. The colors have to be saturated sufficiently so that the primary control graphics (lines, text boxes, simple graphics and buttons) are clearly visible.

Note -- we are also looking at changing the selection mechanism, but there are significant training procedures and manuals in place that make this a much longer term solution.


Colour is a very good cue. When I did some performance testing using 4 servers, we called these pooh, tigger, eyeore and piglet. Each server them got a theme with the relevant characters primary colour. This helped massively when it came to rolling out updates to the correct server.

Be careful of colour blind people, if you have to cater for them, make the theme use a decent contrast colour. The colour doesn't need to be too different, just enough that it is recognise to the user who will immediately notice something is 'wrong' when they come to use the wrong device.

The reason is that we're good at detecting small things that are out of place (possibly due to ancestral survival - our old plains dweller might walk past the same bit of grassland every day and one day notice something different, which would make him stop and look to see the lion getting ready to jump him). However, today we don't care so much :) The operator might come up to the terminal, not notice that the text on top that usually says "device 123" now says "device 456", or he might notice but totally ignore it. So you need to make that visual cue a lot more prominent without being part of the main interface that he uses (or it will become annoying and distracting for him).

Colour background is great for that. An alternative is to have an image for the background, or for a border. If top and bottom of the screen is blue circles, the colour-blind operator may notice them more readily when they've changed to a green triangle pattern, even if he doesn't see the difference in colour contrasts.

  • 1
    Great approach for 4 servers. Though, if you go to a larger number of devices, the memorization curve increases tremendously.
    – dnbrv
    Feb 11 '12 at 19:56

It's safe to assume that some time passes between different users accessing the console and that the system is "idle" between uses (i.e. no physical controls are disturbed). Thus, when the system receives a keyboard or a mouse input after some period of inactivity it can assume that a new user is there and then remind them of the active device by quickly flashing the device number on the screen before fading it into the watermark. This is similar to how TVs used to show the channel number when turned on (maybe still do - I don't use them) and how some OSes identify multiple screens.

The key is to get the idle time measured properly to minimize the possibility of the number being flashed multiple times during one session (in case, a user needs to read some text on the screen). I think 30 seconds is a good starting point. However, if your users change faster than that you'll need to study their behavior and see what they do when they come to the console right after a peer.


What types of visual cues for a GUI screen that can be used to control different devices that can effectively aid users to quickly recognize that the device they think they are controlling is the one actually being controlled?

I think the background color is good. You could also try something like either of the figures below, specially if you have a picture to go with the device. In the diagram below, the unique device number is displayed (I put an example of a device ID of course...). I hope you find this helpful.

enter image description here

  • We thought about this -- but real estate is limited :-(
    – Jay Elston
    Feb 11 '12 at 2:37

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