Blood is a bodily fluid found in the circulatory systems of humans and other animals that carries metabolic waste products away from the cells as well as vital nutrients and oxygen to the cells.
Red blood cells, white blood cells, and platelets are suspended in blood plasma.
The tint of red in the blood varies depending on how much oxygen is present in the red blood cells.
The colour of the blood is red because it contains haemoglobin in blood cells.
Haemoglobin contains a molecule heme which is metal iron in it. When the iron gets oxygenated, the iron turns red and this blood is red.