A lightsaber with a red blade was the weapon of choice for the Lord of Pain, Darth Sion. In 3951 BBY, Sion employed this lightsaber to amputate his former master, Kreia, previously known as Darth Traya.
In that very year, Sion fought Jedi Exile Meetra Surik using this lightsaber in a duel which took place on Korriban. He later fought her once more on Malachor V, which is where he died.