Under which two color names were the first Pokémon games released in Japan?

The first Pokémon games were released in Japan under the names Red and Green.

Pocket Monsters Red and Green launched for the Game Boy on February 27, 1996. The two versions contained different Pokémon available for capture, encouraging players to connect their systems and trade creatures that could not be found in both editions.

Japan later received Pokémon Blue as a special version with revised artwork, code, and dialogue. When the games were prepared for international release, Nintendo used the updated Blue version as the technical and visual basis, renaming the pair Red and Blue for overseas markets.

This explains why many international players know the original generation as Red and Blue, even though the franchise began commercially in Japan with Red and Green. Pokémon Yellow arrived later as a third version inspired partly by the anime.