From "The Sleepover to Restore the Republic", in which Luke Skywalker sets out to steal Anakin Skywalker from Sheev Palpatine. And succeeds.
https://archive.transformativeworks.org/.../114784762
Quote:“Anyway, I kept thinking it over, and since we both want the Emperor gone, we’re basically on the same side, right?” Luke points to himself. “Rebel scum.” He points to Vader. “Also, rebel scum, except you come in black.”
https://archive.transformativeworks.org/.../114784762