“You can see these veins because they lie closer to the surface of the skin. Contrary to a very popular belief, ALL blood in the body is red. Blood carried in the arteries is full of oxygen and is generally a bright red color. Blood that is carried in the veins however, carries more waste products and does not carry as much oxygen and therefore is a darker shade of red. This darker shade paired with the color of the vein itself makes the veins that lie close to the surface of the skin appear blue when looking through the skin.
Amber, RN, EMT-Paramedic”