A lightsaber with a blue blade was used by Jedi Knight Jang Li-Li before and during the Clone Wars, and she was known to wield it.
Li-Li died in 19 BBY when Asajj Ventress, a Dark Jedi aligned with the Confederate forces, obliterated her starfighter. Ventress then searched through the wreckage, locating Li-Li's severed hand firmly grasping the burned hilt of her lightsaber's. She gave this prize to Count Dooku, the Head of State of the Confederacy. Even though Dooku was saddened by her death, he altered the somewhat ruined lightsaber by adding a holorecording device, intending to send a personal communication to Grand Master Yoda.