'Leaf' actually. 'Blue' is the offical name of Prof. Oak's grandson (called 'Gary' in the anime)
It's so much more complicated than that. Oak's Grandson is named Green in Japan and Blue in the West. The FRLG female protagonist for the longest time didn't have an official name. Her manga counterpart was named Blue in Japan and Green in the west. Leaf was a fan name, up until it was canonized relatively recently by the release of a figure iirc.
