I saw a comment here that implied that consumption of the spice (in Dune by Frank Herbert) caused blue lips. Is there any evidence of that? I only remember the blue within blue eyes.
Spice giving its users blue lips is from Frank Herbert's Dune series, which I don't think this is, so you're probably right that it's mixed up with a different book.
There are literally dozens of mentions of the lips of various spice-using characters in original six books of the Dune series by Frank Herbert, short stories and follow-on books by Brian Herbert. Lips are licked, curled, pursed, pouted, patted, parted and wetted on a nearly clockwork basis but none of these mentions are accompanied by any suggestion that the lips are blue or have taken on the same blue tinge we see in the eyes of spice addicts.
The OP may be mistaken for Suk Conditioning which seems to turn the lips a dark purple colour (Yueh is frequently described as having dark or purple lips) or Mentat Conditioning which is often accompanied by heroic consumption of Sapho juice which turns the lips a vivid red colour.
The closest we get to a description of lip colour is in Dune Messiah where we see a description of Korba's lips turning "white with fear", a coloration that would be impossible if they were blue.
It's also worthy of note that in Children of Dune, Farad'n has managed to conceal his spice addiction with the artful use of contact lenses. Obviously this would not be possible if there was a substantial discoloration of the lips:
Farad’n touched his own eyelids, feeling the hard surfaces of the permanent contact lenses which concealed the total blue of his spice addiction.
In Paul of Dune we see a Fremen warrior who has nearly drowned
Enno was completely limp, not breathing. His lips were pale blue, his skin clammy, his eyes closed.
again, this would be consistent with normally coloured lips in a person who had drowned.
The Dune Encyclopedia (considered canon at the time of writing but since de-canonised by Frank Herbert's son) makes no mention of blueing of the lips in its list of symptoms of melange ingestion.
1984
2020 (probably)
No, as far as I remember there isn't any evidence of spice turning your lips to blue. We know that the eyes turn to blue
Extensive use of the drug tints the sclera, cornea and iris of the user to a dark shade of blue, called "blue-in-blue" or "the Eyes of Ibad,"
-- Herbert, Frank (1965). "Terminology of the Imperium: IBAD, EYES OF". Dune. "IBAD, EYES OF: characteristic effect of a diet high in melange wherein the whites and pupils of the eyes turn a deep blue (indicative of deep melange addiction)."
We also see that with Paul. Also:
The taller of the two, though, held a hand to his left eye. As the Emperor watched, someone jostled the Guildsman's arm, the hand moved, and the eye was revealed. The man had lost one of his masking contact lenses, and the eye stared out a total blue so dark as to be almost black.
-- From the first Dune book
But not any mention of the lips turning blue or any color at all.
No. Is it possible that the poster was confusing spice with sapho juice?
Both of these are addictive substances in the Dune universe, and both of them leave marks on the user's body. But the marks are very different in nature: spice stains the user's eyes blue, while sapho juice stains the user's lips red. Neither one is a perfect match for the comment that the question cites, but if the poster mixed them up, that could explain the mistake.
No. In the books it is mentioned at least once that the (only) action taken to disguise spice addiction was to surgically replace the individual's eyeballs with ones from someone not addicted.
