Isn't his HGSS incarnation more evocative of his respective GSC appearance, anyway?
What peeves me off is that the rival's default name in FireRed is "Green" (or at least, the/a player character's default in LeafGreen is "Green"), but they stuck with "Blue" in HGSS, despite his Gym having a green roof (since the city is titularly green) and a green carpet, which, really, they could have taken at least that much time to palette swap it.
On a side note, checking the city at Bulbapedia, "Viridian" is claimed to be a "blue-green" color; clever folk, working at/for Nintendo, I tells ya.