Weird IE thing

picture the scene

user moves mouse over an image, an alt box is shown over the image displaying some helpful text. On friday the atl box showing the text is a white background with black text. Today it’s a black background with white text.

First off I didn’t think you could change this at all.
Second, I didn’t think you could change any settings in regard to this alt box.
Third, first thought was this was an IE setting but it’s happened on everyones machines…perhaps a network setting but this really baffles me

anybody come across this sort of thing or does anyone happen to know how to change the alt box settings :h: