During Mia's famous "overdose" scene, Vincent clearly asks Lance's wife [can't remember her name, she's the one with "all the sh*t in her face."] for a "fat, black magic marker."

Indeed, she does come back with a BLACK magic marker, which, during the closeup of the marker exchanging hands, turns... red!

Then, as previously noted in another slip-up, the big dot disappears. Magic, indeed!