I love that idea. It would let people requiring different contrasts etc see the content too. It won't help with pictures as easily, though a few apps these day

I love that idea. It would let people requiring different contrasts etc see the content too. It won't help with pictures as easily, though a few apps these days do full PDF renders in different colours without much hassle. I am definitely in the no black background white text camp and on the web I have a javascript bookmarklet to zap the colour CSS and make everything rather plain looking. It's not all text for me, but particularly dense text is unreadable, even with my glasses on.