Pokémon Red & Green

In 1996 Pokemon Red and Green were released in Japan and featured the Pokemon Charizard and Venusaur on the covers. Essentially they were the same game as the English Red and Blue, however there are a few differences. Obviously the name and title screen was different for Green, but it was basically what we refer to as Pokemon Blue, with the same version exclusives and the like. Graphically they looked quite different from the English Red and Blue, although some elements can still be seen in these games (the water in the Safari Zone, for instance, looks like the water found in the rest of the game in Red and Green). Most notably are the Pokemon sprites, which had very unusual proportions compared to the art in recent years. These sprites are unique to the Japanese Red and Green and aren't found on any English copy of the game. A few glitches were corrected between the translations, and a difference in coding means they can never connect via Link Cable. The pallet for Pokemon Green on a Game Boy Color was also different, matching the name of the game. Finally, the Unknown Dungeon (or Cerulean Cave) had a different layout that was the basis for the one to return in FireRed, LeafGreen, HeartGold, and SoulSilver.

Pokémon Blue

This is where some of the rumours about Pokemon Green are brought to life. In Japan only there was a promotion through Coro Coro magazine allowing players to purchase an improved version of the original Red and Green that had superior graphics and sound, along with a few tweaks in maps. It was the first of what we now call the "third version", starting a trend of improving the original pairs through a new release. It had cosmetic changes, like shifting the spotlight towards Blastoise on the cover and title screen, a different GBC pallet, and changed Nidorino to Jigglypuff in the opening cinematic. The graphics that players of English Red and Blue are accustomed were borrowed off Japanese Blue. Most notably however it had a totally different set of available Pokemon, many of whom were previously only found in Pokemon Red and Green's in-game trades (which have also been changed). Here are those differences catalogued for your convenience