Why do blood vessels look blue under the skin?
Blood in the arteries is bright red, blood in the veins is dark red mostly from the impurities that are being carried back to the kidneys and liver for disposal that are mixed in and brownish which darkens the red color to more maroon. Blood in veins can look "blue" when viewed through the skin because of light refraction and other factors. But the blood is red and the veins are actually white.When a person donates blood, it comes from a vein, not an artery. It is also not exposed to air, or it would be contaminated and need to be disposed of. It also happens to be dark red, NOT blue.The common misconception of "blue" blood is continued due to textbook illustrators use of blue and red to differentiate arteries and veins. Venous blood is actually a burgundy or maroon color.