A lot of people wanted to know how I did the Backlight mod for my GB. GBC won't work, I've tried it, but the Display is different.
here's the Link: http://der-warst.de/seiten/gameboy-backlight.htm
there has been some discussion on the Yahoogroup regarding this mod and it seems like it's not working with every Gameboy out there because some of them seem have an inverting foil instead of the reflecting tin foil, very much like the GBC.
Cheers, der Warst.
There are also prebuilt backlight modules sold by Nonfinite Electronics which make this modification infinitely easier to perform (though removing the foil layer from the screen is still tricky).
GBCs have also been backlit (more like side- or front-lit) using parts from DSes or SPs.