userstyle challenge

I've been playing around with userstyles that get rid of white backgrounds to make internet surfing easier on the eyes. So far though, I haven't found any global styles that don't hide some buttons and other important elements of many web pages.

What seems to work better is just inverting everything which only has one problem, that being that all the graphics are inverted too, forcing me to change it back if I happen to want to see a picture or watch a video.

So it occurs to me that maybe a user-style might be written that just selectively inverts graphic files back to normal so that you have print inverted but graphics not.

I haven't so far found any such style though. Does anyone know if such a thing is even possible? I don't know much at all about writing styles, so I have no idea but it seems like it would be a great idea!