Why does blood turn dark red as its circulates through the body?

Blood does not turn dark red as it circulates through the body. In fact, the opposite occurs. Blood appears bright red when it is oxygenated and dark red when it is deoxygenated. Oxygenated blood is pumped from the heart through the arteries to the rest of the body, where it delivers oxygen to the tissues. As the blood circulates through the body, it picks up carbon dioxide, which is a waste product of cellular metabolism. The carbon dioxide-rich blood then returns to the heart through the veins. The heart then pumps the deoxygenated blood to the lungs, where it releases the carbon dioxide and picks up oxygen. The oxygenated blood then returns to the heart, and the cycle repeats itself.