Pokémon Red and Green were originally released on the Nintendo Game Boy.
The games used the handheld’s monochrome display and Game Link Cable to let players trade Pokémon and battle one another. That trading feature was central to the series’ design because no single version contained every Pokémon in an easily obtainable form.
Pokémon Yellow later supported the Game Boy and Game Boy Color era, while international Red and Blue also appeared on the original Game Boy. The games’ simple graphics and reusable cartridge format helped them reach a large audience despite the system’s age.
A common mix-up is naming the Game Boy Color, since the series became strongly associated with color versions and later releases. The first Japanese Red and Green cartridges, however, were Game Boy games.