What were the Japanese titles of the two original Pokémon games?

The two original Pokémon games were titled Pocket Monsters Red and Pocket Monsters Green in Japan.

They were released for the Game Boy on February 27, 1996, and formed the first pair of Pokémon role-playing games. The two versions were largely similar, but each contained Pokémon that could not be found in the other, encouraging players to trade through the Game Boy Link Cable.

Japan later received Pocket Monsters Blue as an updated version. When the games were prepared for international release, the overseas pair was called Pokémon Red and Pokémon Blue, using Blue's updated code, artwork, and script.

This is why many international fans know the first games as Red and Blue, while Red and Green are the historically accurate names for the original Japanese release.