The real color of human blood, before it is exposed to oxygen and undergoes oxidation, is a dark red color. This dark red hue is due to the presence of deoxygenated hemoglobin, a molecule found in red blood cells that carries oxygen throughout the body. When blood is oxygenated in the lungs, it becomes bright red in color, but when it is deoxygenated, such as when it circulates through the body's tissues, it appears darker.