I've decided that the reason my Orcs have green skin is because they have two pigments in their skin cells. The first is melanin, which works the same way as it does for Humans, with the amount of melanin affecting how light or dark their skin is. The second pigment needs to be something else, though I'm not sure what, exactly. There are two primary things I want this pigment to accomplish:
- It needs to produce colors other than green. The pigment needs to be able to produce not only green skin but skin of other colors not found in humans, such as red, blue, and purple, potentially more. The idea is that colors other than green are a result of certain genes being more dominant, which usually correlates with certain advantageous attributes, namely greater Arcane or Psionic abilities. So, a red-skinned Orc is likely to be a powerful mage, a blue-skinned Orc is likely to be a powerful Psion, and a purple-skinned Orc is likely to be a Psionic Mage. Thus, these rare skin colors are generally viewed as positive traits, not negative.
- I would like for the green pigment to give Orcish skin somewhat more durability. I'm not sure if skin pigment can do that, so if that isn't feasible, I can have their resilient skin be a result of something else, though I like the idea of the green pigment having an additional function, the same way that melanin helps to protect us from certain types of UV light. I figured in keeping with the "Orcs are durable" idea I'm using, the green pigment could primarily be for making their skin tougher and less likely to scar when it is damaged. This would be why Orcs actually prize their scars so much; if they have one, it means the injury that caused it was not small but they survived it.
I'm wondering if there is something that could accomplish both these things. I was considering having the pigment be copper based. This is because copper is pinkish-orange on its own (which could result in red-skinned Orcs) but is also present in malachite (which is green) and azurite (which is blue.) That just leaves purple, but I haven't been able to find out if copper produces a purple color when combined with something else. However, as it can get three of the four colors I'm primarily after (green, red, nd blue,) it seems the best option for the pigment that gives a majority of Orcs green skin.
Am I on the right track or is there some other compound I should consider for these purposes?