What makes blood red?

HeavyGangsta99940, Only Mr. Spock, the Vulcan, has green blood because his blood is based on copper and not iron like we humans.

I thought blood was blue until it got oxegen

Blood is not red until it comes into contact with oxygen. So then “what makes blood red” the answer would be oxygen.

I answered Oxygen, but the question was "Why is blood red?", not "What makes blood bright red?" Crab blood is blue due to hemocyanin.

Our veins appear to be blue because they have spent their oxygen and are returning to the heart for replentishing...arteries carry the oxygen into our system.

Olliesmommi, no thats a misconception that probably comes from all the charts of veins which to distinguish flow from was put in blue. I thought this for years too quite a shocker.