Green: Info
In Japan, the two original Pokémon games were Red and Green, not Red and Blue like every other country. The difference between Red and Green are basiclly the graphics. Greens graphics are a lot worse then Reds. Japanese Green is the same as American Blue. Also the Japanese Blue (release after Red and Green) is a different game then Red and Green.

One difference in the Japanese Blue game is that they redid the Unknown Dungeon (Which they made the American Unknown Dungeon)