Just wondering. Is there anything that says what color blood Andorians have? I don't suppose there's any canon evidence, but perhaps from books or some other source?
When Shran put a piece of ice through his leg in "The Aenar" or some similar episode, the blood was dark blue in the air. Which incidentally means it's most likely copper.
If it's anything like Klingon blood, it will turn from whatever is canon into something different. So... if you're writing a fanfic or something, it's whatever color you want it to be
The only earthly respiratory pigments I know of that're blue are the hemocyanins (the name is a bit of a giveaway). These are protein structures similar to hemoglobin, but containing a copper prosthetic group instead of an iron one. Hemocyanin is the second most popular group of respiratory pigments on Earth, despite the fact that it kind of sucks (about 1/4-1/3 the oxygen carrying capacity of hemoglobin, depending on conditions and on species). It is well-represented by horseshoe crabs, some other arthropods, and mollusks. The neat thing about hemocyanin is that it's a larger molecule than hemoglobin, so it doesn't have to be cell-bound like hemoglobin is in our corpuscles, in order to prevent filter-jamming in the waste-removal mechanisms. The actual oxygen available to a hemocyanin-using organism in comparison to hemoglobin could actually thus be somewhat competitive, I suppose. At any rate, copper-based respiratory pigment is demonstrably blue when it's oxygenated, and kind of grayish-clear when it's not oxygenated. Since hemocyanin is unbound, it oxygenates in the air, turning dark blue. Like Shran's. Cobalt porphyrins (similar to the hemoglobin porphyrin) have been developed in laboratories, and they seem capable of use as respiratory pigments. However, from what little I was able to find in the last few minutes, they're yellow when deoxygenated and orange when oxygenated. David Darling says this also. Now, why Vulcan blood is green is a mystery to me. It's copper, but green. It's annoying. My best answer is that there's a significant sulfur content somewhere in there, but I don't even know for sure that would effect a green color.
I squished a bug teh other day and it bleeded green, therefore Vulcans is part bug, y'all. The scientific explanation: Ponn Farrrrr! The reasons Vulcans must mate every seven years or die is due to the build up of a certain hormone in their blood which is excreted during the mating cycle. This hormone, called lackanookie in Vulcanian, is yellow and gives the copper-based blood a green hue. Once the mating ritual is performed the yellow substance is neutralized and expelled. Hence, the term making Ponnnn Farrrrr until you're blue in the face. Sector 7, feeling edjamakated.
The writers were thinking of copper statues (such as Lady Liberty herself) which go from brown to green in the open air from verdigris.
My suspicion too--if one believes corrosion on pennies is copper oxide, then it follows (sort of) that oxygenated copper blood would be green (it would also follow under this logic that deoxygenated copper blood would be copper-colored, which highlights the weaknesses of this approach). Now a copper chloride component in the blood, which may or may not be the principal verdigris on Liberty, could contribute to a greener color. I dunno what purpose this would serve, however. I guess I'm a little too sensitive about all this, though. I'll certainly grant that figuring out what colors different chemical compositions make isn't easy. If we had a atmosphere completely composed of hydrogen sulfide, for example, I have no idea what color its sky would be. On another note, Star Trek has a persistent VFX error when it comes to green blooded Vulcans (and blue blooded Andorians). I can't help but notice that their lips and tongues and eyelids and such are still pink.
Arizona is the "copper state," and some natural pools have a definite green color, such as the pools below Havasu Falls.