As you may already know, Game Boy games play on the Game Boy Advance. When you plug in a Game Boy game the GBA detects it and boots up in GBC mode. OK, now here's the tip. Remember, this trick will only work on Game Boy games. It will not work on Game Boy Color or Game Boy Advance games. When a GB game is loaded up the GBA give it a 4 color palette. You can change the palette. On the "Game Boy" loading screen you can press any direction on the D pad or any direction on the D pad + A or B. There are a total of 12 different palettes to choose from, including a super cool negative palette that makes everything look all trippy. While the "Game Boy" screen is on, as long as you keep changing the palette, the game won't continue to load. So don't worry about rushing to picking a color palette. Once you have the palette selected, just stop changing the colors and in about a second the game will load up. It's as easy as that. Now, go forth and mess with the colors on all your old games!