Red blood cells, also known as erythrocytes, are a bright red color. This vibrant hue is due to a protein called hemoglobin, which is responsible for carrying oxygen from your lungs to the rest of your body. Hemoglobin is a complex molecule containing iron, which gives the red blood cells their distinctive color.
Interesting fact: When red blood cells are deoxygenated, they appear a darker shade of red, almost purple. This is why blood appears darker in veins, where it is carrying deoxygenated blood back to the lungs.
