In the image below the deoxygenated blood is represented in _____ colour.
Blue
Human blood is red in colour, ranging from bright red when oxygenated to a very dark, almost blackish-red when deoxygenated. It owes its colour to haemoglobin, to which oxygen binds. Deoxygenated blood is darker due to the difference in colour between deoxyhaemoglobin and oxyhaemoglobin. Here, oxygenated blood is represented in red and deoxygenated in blue colour.