This Instructable documents a cool mod that you can add to your Gameboy Color to give it neat blue lighting effects! And, of course, you better not hurt your body parts or your Gameboy, 'cause I'm not replacing either of them. But hey, this is worth the risk, right?

Step 1: Stuff You Need

And, of course, the ever-needed "Parts" step.
So, you need:
Two LEDs (Color of your choice)
Soldering Iron
Solder
Small Switch
Fine Sandpaper (400 - 500 grit)
Small Wire
Tri-Wing Nintendo Screwdriver or small flathead screwdriver
Transparent Purple Gameboy Color
Helping hands (Optional, but really helpful)
Hot glue gun and glue (Optional)

Step 2: Take It Apart

Now you need to take apart your Gameboy. Flip it over on its front, so the back is facing up. Unscrew the six tri-wing screws. Two are at the top, two in the middle, and two at the bottom, under the batteries. Put these in a safe place.

Lift the bottom half of the case off the top one, then unscrew the three screws near the lower half of the PCB. Make sure you save these.

Once you have that done, you need to disconnect the screen. Lift both black plastic pegs toward the orange ribbon cable at the same time, then lift the cable from the connector.

Step 3: Cut the Switch Hole

Although you don't need to disconnect the PCB to cut the hole for the switch, it's nice to have that out of the way.
Start by scoring the case of the Gameboy in the spot you want to put the switch. I found there is a lot of room just underneath the battery compartment. Cut the hole a little smaller than needed. You can always cut it bigger, but you can't cut it smaller. Keep cutting until you cut all the way through. It takes a long time, but it's worth it for a clean cut.
After you have the hole cut out and the switch fits, drill the holes for the screws. I like to put the switch in first, then drill through the hole for the screw.

Step 4: Diffuse the LEDs

Now it's time to diffuse the LEDs. There are lots of guides on how to diffuse LEDs, so I won't go into great detail here. But you basically just rub the LED on the sandpaper so that the LED looks "rougher". Make sure you get the entire LED, or you will have bright spots.
Why diffuse it? Diffusing the LED makes it not as bright, but makes the light more spread out, which is ideal for this project. Photos three and four show you the difference between a diffused LED and a stock one.

Step 5: Buncha' Soldering

You should now have your Gameboy taken apart, the hole for the switch cut out, and two diffused LEDs. Now it's time to solder it all together.

Take your switch and solder two wires to the switch. I didn't use red and black, but you can if you like. IMPORTANT: Put the switch in its hole before you solder the wires to anything, or you will have troubles later.

After you put the switch in, solder one of the wires to the negative battery terminal labeled BT- on top of the white part of the PCB. Next cut the leads shorter on your LEDs, then solder red and black wires to one of them. Solder the other ends of the wires to your other LED, making sure you pay attention to the polarity. You can tell on the LED which side is positive because the negative side has a flat spot at the base.

Solder the other wire from the switch to the negative side of one of your LEDs. You should have something like in the sixth picture.

Finally, solder a short wire from the positive side of your LED to the positive battery terminal, labeled BT+. My LEDs are rated for 3.1v, but if your LEDs are rated for a lower voltage, you may want to add a small resistor (100 Ohms) to extend the life of them.

You should now have everything soldered together! Flip the switch and see if everything lights up okay. If not, check all your connections, and make sure you have the polarity right on your LEDs.

You may want to insulate the connections to the LEDs, but I didn't find a problem with it.

Step 6: Get It Back in One Piece

Now comes the really hard part; putting it all back together. First, connect the screen ribbon cable. This is kind of hard, especially if you're trying to take a picture at the same time. :P Make sure you lift the plastic pegs up, then put the ribbon cable in, then push the pegs down again. Next put all the buttons back in, and put the pads behind them. Quickly push the PCB against them, so they don't fall out. Then screw those three screws back in to the correct holes, which are conveniently labeled with little circles around them.

Finally, screw the back cover on again, and you're finished!

Sorry the first picture is out of place, I just wanted a good "main" image. :P

Step 7: Admire

Go into a dark room, shut the door, and flip on your Gameboy light! The game can be run at the same time as the lights, just so you know.

Thanks for reading, and enjoy your neat mod!