Red lightsabers are the weakest, according to a Star Wars study conducted at the University of Leicester regarding lightsaber colors.
Decades of Star Wars lore has dictated that the red lightsabers favored by The Sith offered greater offensive capabilities than the softer colors favored by The Jedi.
One wonders what Star Wars: The Last Jedi will have to say on this subject.
Surprisingly, their findings indicate that the red lightsabres favored by The Sith are physically the weakest of all lightsaber colors.