Shiny Pokémon are incredibly rare, alternately colored versions of Pokémon. In FireRed and LeafGreen, the odds of encountering a shiny Pokémon are 1 in 8192. There's no specific method to increase these odds, so finding one is purely based on luck and persistence. Many players engage in 'shiny hunting' by repeatedly encountering or resetting for specific Pokémon. While challenging, finding a shiny Pokémon is a highly rewarding experience for collectors.
