Why does it change colors?

I've looked around for the answer to this and I don't seem to see it (though I also looked for the label printer this morning for 15 minutes before my boss found it right where it should be!). Why is the gadget sometimes grey background and sometimes brown? I have it set to the "Default" color, but I can't help wondering what it means.

Thanks for satisfying my curiosity (and supplying me with a great gadget).

Well, I have absolutely no idea, I have never seen it changing background colors.

If you can tell me in what situations it changes backgrounds, I might find out what is going on.