Blood is red. While the shade can vary from a bright cherry red to a darker brick red, it's always red. This is because of the presence of hemoglobin, a protein in red blood cells that binds to oxygen.
- Oxygenated blood (blood that has picked up oxygen from the lungs) is a brighter red.
- Deoxygenated blood (blood that has delivered oxygen to the body's tissues) is a darker red.
It's a common misconception that blood appears blue in veins. This is due to the way light interacts with our skin and the veins beneath. Veins are actually translucent, and the darker red color of deoxygenated blood appears bluish through our skin.
