The element primarily responsible for the color of hemoglobin is iron. Hemoglobin, a protein found in red blood cells, binds to oxygen molecules and transports them throughout the body. Each hemoglobin molecule contains four iron ions, which play a crucial role in its ability to bind oxygen. The presence of iron gives hemoglobin its distinctive red color when it is oxygenated. Deoxygenated hemoglobin appears darker, showing a bluish hue due to the way light interacts with the protein. This dynamic color change is essential for the efficient transport of oxygen and is vital for sustaining life in organisms.