✔ 最佳答案
Because hemocyanin does not work very well as an oxygen carrier, in the blood of endovertebrates.
Women, having their vertebrate skeletons "inside" (endo-) their bodies, are therefore endo-vertebrates and, thanks to evolution, have their oxygen supply brought to the different parts of their bodies by the more efficient hemoglobin (iron-based, red in color) instead of hemocyanin (copper-based, blue-green in color) as is the case in some non-vertebrates (e.g., mollusks).
Of course, there is always the option of using a green colored cosmetic foundation. In older times, the greenish coloration was reached by using foundation using copper oxide.
Copper oxide is also called "vert-de-gris" - the same stuff that gives copper roofs and statues this green color called "patina", even though they are... err... "copper-red" when they are brand new.
Putting vert-de-gris foundation on the skin has never been healthy for the skin, especially if left on the skin too long (poisoning by metal salts caused when the copper oxide reacts with the acidic sweat).
So look for modern non-copper-based colored foundation, then find someone willing to use it.
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Vulcan women (fictional - Star Trek) have a greenish tinge to their skin because of their "copper-based blood".