This is a Gameboy Color that I modified with the frontlight of a Gameboy Advance SP. I also painted it and added NES buttons…
Best thing about it is that I was able to wire it up so that the frontlight turns on and off with the gameboy, no extra switch 
I also replaced the GBC speaker with one from one of my broken SPs, I can kind of tell that it sounds a bit louder, but I may be imagining things.
Hey Zachariah, I am in the process of modding my gbc (sp frontlit) and have it working but.. the light is very dim. I am using a 33ohm resistor (at least I think i am) and think that may be part of the problem. The resistor I grabbed from an old arcade monitor board. Do you have any insight into this problem? Thanks.
If you’re wiring straight to the battery terminals, you shouldn’t need a resistor. Try removing it. The frontlight runs on 3v, so you should be good to go. I made a small how to on instructables. Here’s a link. Click this