Yeah Terra's original name in Japan was "Tina" & she was a blond. Personally I feel they improved her when FF6 came state side, Green hair plus the name change to Terra offered a much improved character concept & made her more individual & memorable.
Had they kept her as a blond Tina....she just would've been another bland face lost in the croud like Bartz from FF5 or Aris from FF7.