From Bulbapedia, the community-driven Pokémon encyclopedia.
This is a list of Pokémon by their color according to the Pokédex. While the actual colors of the Pokémon species can vary, the color listed in the Pokédex is usually the color most apparent or covering each Pokémon's body. No orange category exists; Pokémon that are primarily orange are listed as red or brown. Prior to Generation VII, Pokémon with multiple forms, such as Wormadam and Shellos, were categorized into their most common form's color. Several Pokémon are placed in categories that hold little resemblance to their perceived color, or which would be more logically placed in a different category. One example is Bronzong, who, while considered by some to be predominantly blue, is placed in the green group; this particular case may be attributable to the ambiguity between "green" and "blue" in the Japanese language. Also, some species are categorized on the basis of the color of their heads or faces, such as Druddigon, which is categorized as red despite being mostly blue.
Besides its use in the Pokédex, a Pokémon's color only has an aesthetic effect with the exception of the Festive Feud Wi-Fi tournament, where only red, white, or green Pokémon could compete.
In Generation VII, the color of several species of Pokémon with multiple forms were changed.
List of Pokémon by color