Instead of using iron, their blood uses cobalt and vanadium

And when their blood is exposed to certain gasses, like normal O2, and has sunlight or moonlight shined on it, turns a perfect sky blue, like literally whatever shade the sky is at that moment Whereas when it comes in contact with O3, or ozone, it turns a bright green due to it slowly oxidizing them from the inside out, which is very painful; Fun fact: ASCII-oid blood is clear and mildly more viscous due to them breathing nitrogen