>>20705646Because the original two version of Pokemon were Red and Green, and Blue was a third version with gameplay improvements due to the first two being super buggy. The english speaking world got two modified versions of Blue to replicate Red and Green with the improved gameplay. Because of this, the Rival was originally called Green, but they decided to go with Blue in the english territories to represent the renamed games.
The female character was named Blue, but when she made her way west, the name Blue had already been pasted onto Green, so they just swapped the names around. The original names are still Green for the Rival and Blue for the female.
Also, Leaf is to Blue as Kris is to Crystal.
