Why is oxygenated blood red and non oxygenated blood maroon?

Oxygenated blood is bright red due to the presence of hemoglobin, which binds to oxygen and reflects red light when it is oxygen-rich. In contrast, non-oxygenated blood appears darker, or maroon, because hemoglobin changes shape when it releases oxygen, altering the way it absorbs and reflects light. This color difference helps indicate the blood's oxygen content as it circulates through the body.