Contrary to popular opinion, blood is always red whether it is oxygenated or deoxygenated. Scientific diagrams often express oxygenated blood as red and deoxygenated blood as blue, however this is more for demonstrative purposes than an indication of actual biological color.

While blood can play different functions based on whether it is oxygenated or not (i.e. the right side of the heart pumps deoxygenated blood while the left pumps oxygenated blood), the color itself remains either dark or light red.

Why is this? Well, red blood cells contain the protein hemoglobin, which carries oxygen from the lungs throughout the body. Deoxygenated cells still have hemoglobin, just without the oxygen. At the center of each section of hemoglobin is an iron atom, which allows the protein to carry oxygen when it is present, as well as giving it its distinct red color. When this iron atom is not bound of oxygen, the way light reflects off of it changes, making it appear darker. Therefore, oxygenated blood is light red while deoxygenated blood is dark red. Thanks for your curiosity!

Blood is actually red all the time, but different colors of red. When you see blood outside the body it is usually a dark red. This blood is from the veins. Sometimes you may cut an artery. This blood is bright red because it has picked up oxygen in the lungs. It also spurts out in pulses instead of oozing like the blood from veins. (What's the difference between veins and arteries? Why does arterial blood spurt?)

The blood vessels you see at the surface of your skin are veins. Skin color varies a lot, so the veins can look different in different people, but blood is exactly the same color in everyone. It still doesn't look red in veins. That's because we're seeing the *walls* of the veins too. When you see lemon-lime flavored soft drinks in plastic bottles they usually look green, because the bottles are green. But when you pour them out, they're often clear or yellow. So when we look at our veins, the color we see depends on the color of our skin and the walls of the veins.

Why do you think we don’t have arteries close to the surface of our skin?

Assuming you are talking about human blood, blood is always red. (Some animals have different color blood – blue and green!) Our blood gets its color from hemoglobin, which is an important part of your blood. Hemoglobin helps the blood carry oxygen and carbon dioxide which is important for your ability to function. Hemoglobin has iron, which gives it the red color.

When the blood is oxygenated it is bright red. When it has depleted its oxygen, blood is dark red.

Blood appears blue-ish in your veins because the skin blocks light. What you see is the blue color being reflected back to your eye.

Hi Bill. I'm sure you have heard that blood is blue in our veins before it hits oxygen but that it not true. Blood contains a protein, Hemoglobin, and hemoglobin binds Iron. Blood looks red because we are seeing the proteins carrying Iron. This iron is present regardless of blood's contact with oxygen. Therefore, the correct answer is that blood is dark red before it hits oxygen and lighter red when it does.

The color of human blood is red. In our veins, without oxygen, the color would be a dark red. If you're curious as to some of the veins on our bodies look blue through our skin, there was actually some research on how light interacts with skin to make that color! A 1996 research article in optics summarized that the blue color has to do with how different colors of light absorb and reflect, and how deep the veins are. In short, blue-looking veins do not equal blue blood.

The color of blood until it hits oxygen is dark red. Oxygenated blood is lighter red.