>>56514816Blue was initially given as a bonus for subscribers of the CoroCoro Magazine who filled and sent a form in Japan.
It came out a few months after Red and Green as basically a slightly enhanced version that changed all the Pokemon front sprites, corrected a few bugs, had different Pokemon in the intro (Gengar fighting Jigglypuff instead of Nidorino) changed a few tilesets and had slightly different encounter tables (as well as slightly different Pokemon prizes at the Game Corner and different in-game trades).
Shortly after, GameFreak and Nintendo were discussing the terms of a contract to release Red/Green in the US.
Someone thought it'd have been a better marketing move to release them as Red and Blue instead, as those are the colors of the US flag.
They used Japanese Blue as a base, since it was an updated version of Red/Green, and basically tweaked and split it into an enhanced version of the og Red and Green. They kept Nidorino in the International Red intro, but replaced it with Jigglypuff in Blue (whereas Green doesn't have a different intro than JP Red).
This caused a few mistakes in the process, which is why for instance there's an NPC claiming Raichu evolved upon trade (that's because they retained the text from JP Blue, but changed the trade to how it was in Red/Green, where a Graveler was requested instead of Raichu).
Blue was mostly distributed as a bonus version to celebrate the milestones of Red/Green selling 1 and 4 millions of copies in Japan, and wasn't actually sold in Japanese retail stores until the end of 1999.
