IE has implemented the media query -ms-high-contrast to allowing selecting based on the usage of a black-on-white or white-on-black high contrast mode: http://msdn.microsoft.com/en-us/library/windows/apps/hh465764%28v=vs.85%29.aspx It's currently a feature request for Media Queries Level 4: http://wiki.csswg.org/spec/mediaqueries4#high-contrast-mode In addition to this being an important accessibility feature for the web, we also want to use it (sooner rather than later) to help improve Firefox's UI.

I recall a recent bug (though I can't find it) with discussion about adding a media query that we decided not to add because we didn't want to expose that information. I'm wondering whether that's also an issue here, although I suspect it's not because I suspect that high contrast mode is also detectable through computed style given that we make it flip the color overriding prefs.