system
Given the following post, respond as if you're commenting on Reddit:
human
Why don't we have green or blue or other color people?
gpt
This answer may be simpler than you are looking for, but humans' skin color comes from melanin. The amount and placement  of melanin in the skin is determined by genetics, this is why some people are darker than others when they don't get as much sunlight or why some people freckle note than they tan or vise versa. Melanin is dark brown in color while all skin without melanin is a semi translucent white thats a bit pink over a body,so the only possible color range is from white-pink to very dark brown.