Is there a lot of canon about why Vulcan blood is green? I'm no chemist but it seems a bit fanciful to me*. Horseshoe crabs have blue blood because their blood is based on copper instead of iron. What kind of blood base would turn green on oxygenation?
*yes, yes, I realise how ridiculous it is
I thought horseshoe crabs have blue blood because they're arthropod royalty.
(Hoo boy, I'm on a roll! Somebody stop me!)