Game Boy Color System Cheat Codes for Gameboy

In-game reset
While playing a game, press A + B + Start + Select to reset most Game Boy and Game Boy Color games.

Invert colors
At the Game Boy logo, press Right + B to reverse the screen and sprite colors. This may make the game easier to see in dim light.

Other colors
Other color schemes (as stated in the manual) may be selected at the Game Boy logo by pressing the following combinations: Up: Bright Red
Up + A: Red
Up + B: Dark Red
Down: Pastel
Down + A: Orange
Down + B: Gold
Left: Bright Blue
Left + A: Dark Blue
Left + B: Grey
Right: Bright Green
Right + A: Dark Green
Right + B: Invert Colors