Prior to the release of Pokémon LeafGreen in North America and Europe, various alternate titles were rumored, possibly to stay consistent with the titling of Pokémon Blue in those countries. These rumored names included Pokémon WaterBlue, OceanBlue, and AquaBlue.
WaterBlue has also been rumored to be the third version of Pokémon FireRed and Pokémon LeafGreen, as Emerald is to Ruby/Sapphire. Nintendo has not made any indications that this is true, however, and has announced Diamond and Pearl as the next Pokémon games to be released.
Some people note that a "WaterBlue" or "ThunderYellow" third game are not necessary. All 150 Pokemon can be found between the two versions, and the Hoenn games (Ruby, Sapphire, and Emerald) allow all 386 Pokemon to be collected. However, some offer the counter argument that this was also true of Red and Blue, and that releasing a "special edition" in each generation has become something of a tradition.
An unofficial ROM hack of FR/LG, titled Pokémon ThunderYellow, was created and distributed among various Pokémon forums.