Shiny Pokémon are a different color than that Pokémon normal for their species. Some examples would be a yellow Bulbasaur (they are usually greenish-blue) or a red Gyarados (they are usually blue). They are extremely rare; there is only a 1 in 4,096 chance of an encountered Pokémon being shiny, but there are ways to improve your chances of obtaining one, which vary per game. Some Pokemon in the same evolution line have different shiny colors, even if their regular colors are the same. For example, Ponyta and Rapidash normally have reddish-orange flames. However, shiny Ponyta have blue flames while shiny Rapidash have silver flames.