So I came to this weird realization that based on my headcanons, it would make most sense for Pit and Dark Pit to bleed some copper-colored substance because it's metallic orange and you get metallic orange color if you mix metallic yellow (ichor) with red (blood).

Alternatively angels could just have copper-colored fluid running in their veins to symbolize how they're somewhere between gods and humans, because I like this idea way too much to not use it outside my headcanons