Like say you wanted to unleash an army of synthetic humans who are essentially programmed to sexually service people who don't get laid and you want them to stand out from real humans? Or at that point do we just give them pink skin or something?
IIRC blue is actually unnatural in living creatures so that.
Blue "color" is not. Lots of animals have it, especially birds. As far as blue pigment goes, there's a butterfly that has one. I think there's a few sea creatures that are also genuinely blue.
It says right here in Matthew 16:4 "Jesus doth not need a giant Mecha."
https://i.imgur.com/dQgC4kv.jpg