What were the original Japanese names of the two 1996 Pokémon Game Boy versions?

The original Japanese Pokémon Game Boy versions were Pocket Monsters Red and Green.

These paired role-playing games launched in Japan on February 27, 1996. Each version contained Pokémon that could not normally be obtained in the other, encouraging players to connect their Game Boys and trade with one another.

Japan later received Pocket Monsters Blue, a revised edition with updated artwork, dialogue, and other changes. For international markets, Nintendo used the revised Japanese Blue material but released the games as Pokémon Red Version and Pokémon Blue Version.

That localization history is why many players assume Red and Blue were the original worldwide pair. They were the international names, while Red and Green were the original Japanese versions. Gold and Silver belong to the next generation and were released in Japan in 1999.