Why do veins appear blue beneath skin when blood is red?

Question:

When one sees a vein through their skin, in arms and legs for example, the veins appear blue in color.

Answers:
In humans and other hemoglobin-using creatures, oxygenated blood is a bright red in its color. Deoxygenated blood is a darker shade of red, which can be seen during blood donation and when venous blood samples are taken. However, due to an optical effect caused by the way in which light penetrates through the skin, veins typically appear blue in color in light-skinned people. This has led to a common misconception that before venous blood is exposed to air it is blue. The appearance of blood as dark blue is a wavelength phenomenon of light, having to do with the reflection of blue light away from the outside of venous tissue if the vein is @ 0.02in deep or more. This is due to the difference in color between deoxyhemoglobin and oxyhemoglobin; the red color ultimately originates from the iron atom in heme. When red blood cells die, the hemoglobin within them is released and broken up: the iron in hemoglobin is salvaged, transported to the bone marrow by a protein called transferrin and used again in the production of new red blood cells; the remainder of the hemoglobin becomes a chemical called bilirubin that is excreted into the bile which is secreted into the intestine, where it gives the feces their characteristic yellow-brown color.

Veins are closer to the surface of the skin and so you are able to see them if you have light skin. Arteries can sometimes be seen in a light-skinned baby.

"Blue blood" in the sense of "aristocracy" is actually a direct translation of the Spanish phrase "sangre azul." The oldest families of Castile in Spain prided themselves on the "purity" of their lineage, believing it never to have been "contaminated" by Moorish, Jewish or other "foreign blood," and as evidence offered the blueness of their veins against their fair complexions. In truth, their blood was the same color as everyone else's, and it was simply the lightness of their skins that made their veins appear blue, but "sangre azul" was taken into English around 1834 as "blue blood" and has been a synonym for "nobility" or "aristocracy" ever since.

Other Answers:
It's all about the oxygen and when the blood hits the oxygen.

Blood is blue but when it hits AIR it becomes red When the blood touches oxygen out side your body it turns red.

isn't blood blue in your veins, but when it is exposed to air it turns red?

i dont know, i could be making that up

blood is blue or very dark red like purple until the air hits it then it becomes lighter.

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Why do veins appear blue beneath skin when blood is red?

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