Why is vein green?

The blue of veins is visible due to the interaction of light with the skin, the amount of oxygen in the blood and other factors.

Vein causes are blue

Blood flowing in the body is bright red or dark red depending on the amount of oxygen in the blood; The veins themselves are not green, they are only green when seen through the skin. This blue is seen by four factors.

Vein colors are dominated by many factors.(Photo: iStockphoto)

The first is the interaction of light with the skin in multiple wavelengths, equivalent to different colors. Light passes through the skin, absorbed and emitted back into the environment. The process of absorbing and radiating backwards takes place thousands of times in the blink of an eye.

Scientists found that the veins emit a lot of blue , and only a very small amount of red, so we often see veins are green.

The second factor is the amount of oxygen in the blood that affects the blood color and ability to absorb light. Oxygen is transported by red blood cells. A maximum red cell can carry four oxygen molecules. Under the surrounding effect such as high temperature, acid environment, one or more oxygen molecules will leave the red blood cells to make blood dark. This crimson color is still red in nature but easier to look into.

The third element is the vein itself, especially its diameter and position . If the veins are located just under the skin, they will be red. The deeper you go, the color of the vein will gradually turn blue. Meanwhile, the vast majority of veins lie more than half a millimeter below the skin. This optical phenomenon is related to complex blood transport equations.

Scientists have also observed a bit of green in arteries, but less, because the blood in the arteries is bright red. When light passes through the skin, the color difference between the veins and arteries will be amplified, so we see a green veins. Besides, arteries are usually small and deeper than the skin so they often don't see arteries.

The last factor is the brain. Information collected from the retina to the brain is handled a lot. For example, purple is not always purple, when you put purple next to red, your brain will turn purple into blue. In the case of veins, the contrast of the surrounding skin also tends to make the veins appear green.