We know that Vulcan blood is copper based instead of iron as in Humans, making it appear green instead of red. This is shown when bruised or bleeding as well as in Bones' insults to Spock.
The lips of (especially Caucasian) Humans are red(dish) because the blood shines through the skin. Consequently, Vulcan lips should be green:
Is there a decent explanation why this is not the case, both In-Universe as well as Out-Of-Universe? This would be a terribly cheap thing to do, while making Nimoy look even more alien than the ears and eyebrows alone. The fact that Spock's blood is green was established very early in the series if I remember correctly, so it is safe to assume they planned it all along.