Question

In a coloured diagram why do we generally show pulmonary artery in blue and pulmonary vein in red

Answer 1

it is for recognition blue indicates deoxygenated blood and red is oxygenated blood

Answer 2

Generally we show Pulmonary artery in blue and Pulmonary vein in red because of Pulmonary artery which is a artery that takes impure blood to the lungs or deoxygenated blood to the lungs and that blue colours shows that deoxygenated blood and in case of Pulmonary vein it shows that the pure blood or oxygenated blood from the lungs is taken back to the heart for supplying it to different parts of the body through the Aorta and that red colour indicates that oxygenated blood.