Pink Lightsaber Syndrome, or PLS for short, is an ailment that mainly afflicts Dark Lords of the Sith, during their old age. No one knows where it came from, and no one has really bothered to study it. Fortunately for the Sith Order, the disease is actually very rare; only two three Sith Lords were known to have contracted it: Palpatine (early onset) and Darth Cool (full-blown PLS). Darth Vader later contracted the disease from his Master.