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Human blood is red because of the iron in the haemoglobin. This gives red blood cells their red colour. Veinous blood is much darker than arterial blood, and your teacher is right that oxygenated (arterial) blood is 'redder' than deoxygenated (veinous) blood. However, human blood is not blue. Some animals do have blue blood though.
It's not made in a kitchen, but blood has ingredients, just like a recipe. Your body doesn't go to the store to buy those ingredients. It makes them. Bone marrow â that goopy stuff inside your bones â makes the red blood cells, the white blood cells, and the platelets. Plasma is mostly water, which is absorbed from the intestines from what you drink and eat, with the liver supplying important proteins.