Although Red Blood flows throughout the body, human body veins appear green or dark bluish color through the skin or blood vessels, asked in some Medical Assistance Program.
Research and studies from medical technology states, “There is no vein either Green or Blue in color“. It’s because of their location within the body.
Hemoglobin present in RBC (Red Blood Cells) is the reason for red color, and this carries oxygen from lungs to all the blood cells and take away carbon dioxide from blood tissues to lungs.
This Hemoglobin appears different in colors when oxygenated and deoxygenated in certain locations of the body.
When blood carries high amount of oxygen, it reflects red color and when carbon dioxide concentration is higher, it reflects blue color. Thus, mixing these high amount of carbon dioxide and oxygen with yellow color of fat and when, blue color of sunlight is reflected (as all other colors are absorbed by skin) from skin, it ends up with blue or green color.
Likewise, the same veins appear different in color when observed other than the skin surface.
One of the reason why veins are closer to the surface of the skin is, they play a vital role in heat exchange with outside environment.
Veins acts as reservoir of blood. About two-thirds of blood volume is present always in veins at the given time because of regular circulation.
Even Arteries (actual color is reddish-brown) may appear blue when observed through the surface of skin.