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The blood inside your veins is dark red. So, many people wonder why veins look green or blue through the skin instead of red.

Veins are types of blood vessels. The other blood vessel types are capillaries and arteries. Blood vessels help transport blood and nutrients throughout your body.

The job of most veins is to carry oxygen-depleted blood from bodily tissues back to your heart. Your pulmonary artery brings your blood to your lungs, where it receives a fresh supply of oxygen. Your arteries then carry the oxygenated blood to your tissues and organs.

In this article, we’ll explain why veins can look green or blue, particularly through lighter-colored skin. We’ll also go into detail about vein symptoms that require medical attention.

There are three types of veins: deep veins, pulmonary veins, and superficial veins. Superficial veins are the type that you can see.

They may look green instead of red because the color green has a shorter wavelength than the color red. They may also look blue or blueish-green because blue also has a shorter wavelength than red.

The electromagnetic spectrum contains wavelengths, or visible light that your eye can see. The colors of visible light range from red to violet in this order: red, orange, yellow, green, blue, violet. Red has the longest wavelength, lowest frequency, and least amount of energy.

What we perceive as “color” is actually the frequencies of the visual light spectrum that are reflected from a surface while other waves are absorbed. For instance, a green leaf reflects the green waves and absorbs the other colors, which is why we see it as green.

The illusion of “green” or “blue” veins occurs because you’re viewing them through layers of skin and tissue, which absorb more of the red frequencies while allowing higher frequency waves to reach your eyes.

Role of skin pigment

If you have light skin with less pigment, you may be more likely to see green, blue, or violet-colored veins.

If you have dark skin with more pigment, it can be harder to see the color of veins. Skin with more pigment evolved in part to protect veins from harsh sunlight and solar radiation. Skin that has more pigment absorbs more light than skin with less pigment. This makes it harder to see vein color.

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Superficial green veins may be most visible on specific parts of your body and face such as:

  • backs of hands
  • shins
  • thighs
  • abdomen
  • chest
  • forehead
  • neck

Green and blue veins can also be seen where your skin is thin. Skin can become thinner and less elastic with age, making veins appear more prominent. Also, the less fat you have, the more your veins may show, regardless of your age.

Other reasons why veins may be more visible

Here are some other reasons why veins may appear more prominent:

  • Genetics can play a role in how visible your veins appear. For example, if one of your parents has noticeable veins, you may have them as well.
  • Emotion can also have an effect. If you’re angry, yelling, or laughing uproariously, an increase in pressure may make your veins expand and bulge. This may be most likely to occur on your forehead, temples, and neck. Sneezing can also have this effect.
  • Exercising can also raise blood pressure, making veins more prominent.
  • Heat and hot weather can cause veins to expand and dilate, making them more visible.

Visible green veins are usually nothing to be concerned about, unless they’re accompanied by other symptoms such as:

Medical conditions characterized by visible veins include:

Varicose veins

Varicose veins are caused by a malfunction in your one-way valves that stop blood from flowing through your veins backward. Varicose veins often appear on your lower legs.

Since they’re engorged with blood, varicose veins may look enlarged and swollen. They may look like zigzags, and take on one of the following colors:

  • blue
  • red
  • purple

Varicose veins can be painful. They may also make your legs feel:

  • heavy
  • itchy
  • tired

Pregnant people and people over 50 assigned female at birth may be more likely to get varicose veins. People with obesity may also be prone to this condition.

Spider veins (telangiectasia)

Spider veins aren’t green. They appear as tiny, threadlike red or discolored lines under your skin, in areas such as your:

  • nose
  • cheeks
  • fingers

Spider veins sometimes hurt or itch.

They may indicate a serious underlying condition, such as alcohol use disorder. In many instances, they’re caused by aging blood vessels or by behaviors such as sitting or standing for long periods of time. Pregnancy can also cause spider veins.

Superficial thrombophlebitis

Superficial thrombophlebitis is an inflammatory, short-term condition caused by a blood clot under your skin.

Symptoms include:

  • redness or discoloration
  • warmth
  • hardening of a vein
  • darkening of your skin
  • pain
  • inflammation

Superficial thrombophlebitis is often caused by insertion of an intravenous (IV) needle. It may also result from varicose veins.

Since it occasionally leads to a serious condition called deep vein thrombosis, you should always call a doctor if you suspect you have superficial thrombophlebitis.

Green veins are superficial veins located near the surface of your skin. They appear green instead of red because green has a shorter wavelength than red.

You’re more likely to see green or blueish-colored veins if your skin is a lighter color. If you have darker skin, it can be harder to see the color of your veins.

Green veins aren’t indicative of a serious condition unless they’re accompanied by other symptoms, such as:

  • swelling
  • inflammation
  • pain

If you’re experiencing any of the above symptoms, talk with your doctor. They can diagnose and recommend treatment for any vein-related conditions you may have.