Pokémon Red and Green were first developed for the Game Boy.
Game Freak designed the original role-playing games around Nintendo’s monochrome handheld system. The Game Boy’s portability made it possible for players to carry their collection, while its Link Cable enabled trading and battles between two systems.
That trading feature was central to Pokémon’s design. Red and Green contained different Pokémon, encouraging players to connect their Game Boys and exchange creatures that were unavailable in the other version. This helped turn a single-player role-playing game into a social collecting experience.
The original Japanese games used the Game Boy, although later Pokémon releases expanded to the Game Boy Color and other systems. International players often remember Red and Blue rather than Red and Green because Blue replaced Green in most overseas markets.