Instructions
Load your game after entering the Shiny Pokemon Action Replay cheat. Start a new game or continue a previously saved game.
Press "X," then highlight the "Trainer Card" option using the directional pad. Press "A" to look at your Trainer Card.
Press "R" and "A" at the same time while viewing your Trainer Card to activate the Shiny Pokemon Code. This turns all Pokemon, including your captured Pokemon and those encountered in the wild, shiny.