Green was paired with Red in Japan’s original Pokémon game release.
Pocket Monsters Red and Green launched for the Game Boy in Japan in February 1996. The two versions shared the same overall adventure but included version-exclusive Pokémon, encouraging players to trade with one another.
International players often expect the original pair to be Red and Blue because those were the versions released outside Japan. Japan later received Pokémon Blue as an enhanced special edition, and the international Red and Blue games used that version’s updated programming and artwork while retaining the original Red and Green Pokémon distribution.
Pokémon Yellow followed as an enhanced edition with Pikachu in a central role and stronger visual connections to the anime. Thus, “Red and Blue” is correct for the familiar international release, but “Red and Green” is the historically accurate answer for the franchise’s first Japanese game pair.