Green-blooded Bastards: An Argument Against Hemocyanin
That spawned an analysis of the differences in hemoglobin and hemocyanin, and raised the burning question, “If Spock’s blood is really copper-based, shouldn’t it be blue, instead?”
I won’t be rehashing the entire conversation. My friends @elsa-lost-in-translation, @outside-the-government, @starshiphufflebadger, and @gracieminabox each made some excellent points, which you can read if you follow the links.
I’m here to tell you, in a word -
Spock’s blood is green, dammit, and his skin is… well, what we see in TOS. Fleshy-pinkish-yellow-funky-almost-jaundiced-looking-greenifyousquint.