Your Blood Is Red, Not Blue
In school, teachers taught that deoxygenated blood, which means the blood running in our veins before it’s exposed to air, is blue. As cool as it would be to have blue blood running through your veins, this is simply not true. Your blood is dark red. If you look at your veins, you might think your blood is blue. Our blood contains hemoglobin, a complex protein that contains iron. When iron reacts with oxygen, it turns it red. Even though the color of red may vary, depending on how far away from the heart it is, it’s never blue. It only appears blue because of how light travels through the skin. All of those diagrams they gave us about blue blood in science class was wrong. The only living creatures that have blue blood are octopi, crustaceans, and squid (Reddit).