Human blood is red, ranging from bright red when oxygenated to dark red when not. It owes its colour to hemoglobin, a metalloprotein compound containing iron in the form of heme, to which oxygen binds. There exists a popular misconception that deoxygenated blood is blue and that blood only becomes red when it comes into contact with oxygen. Blood is never blue, but veins appear blue because light is diffused by skin
No. The vein is so blood looks blue. air has nothing to do with it. When you get your blood tested the blood inside the tube is red and the tube is air-free. The blue blood thing is just misconception.
Kind of. It all has to do with oxygen in the blood. Your arterial blood is red because it has oxygen in it. The lungs oxygenate your blood, it goes through the heart and into the arteries and gets delivered through the arterial system to the body. The veins bring the unoxygenated blood back to the lungs. Look at your hands and see how the veins are blue. That is because it is not oxygenated. As soon as oxygen hits blood it turns red. So, even though blood is drawn by a lab from a vein, as soon as it exits your body it hits oxygen, and that is why the blood in the tube is red. (Found this on the internet) (I think it's a myth)