If the blood is red, why do the veins look green or blue?

Surely you have ever asked yourself the question about why we see blue or green veins, but the blood is red. A response that has much of its explanation in the light compartment, once it comes into contact with our body, but also in the properties of blood.

To begin, we must briefly explain the wavelength and how it affects colors. Once we understand this factor we will have everything necessary to understand much better what happens when the light passes through our skin. The red light has a long wavelength, that is, 700 nanometers. For its part, the violet light has a short wavelength, 400 nanometers. The light we receive during the day is white, a mixture between the different spectra of visible lengths.

Now, when red light enters our veins, it is absorbed by hemoglobin. To be more precise and better understand the process, hemoglobin is the protein that makes our blood turn red. An example and that we all have ever done as children is to put our hand in front of a red light. Due to the absorption of light and hemoglobin, the hand will turn completely red, while the veins are marked in darker areas. It is a process that has its application in medicine, used by doctors to draw blood by illuminating the specific area of ​​the arm.

Veins on the foot. Image: iStock

But what happens to the blue or short length light? In this case, the blue light deviates much more easily than the red light and therefore does not penetrate the skin. Returning to the previous example of the light on the skin, in case it is blue it will only turn our skin into that color, making it very difficult or practically impossible to locate the veins. As a curiosity, not a few locals use blue light for their bathrooms to prevent the use of intravenous drugs.

Now that everything starts to make sense and we have part of the settled theory, it is time to ask ourselves: what would happen if we applied blue and red light at the same time on the skin? We would have an impact of colors reflected between blue, red and different ranges. Although the effect varies depending on how deep or thick your vein is, the result is none other than in places where there are veins you will see less red and therefore more blue, thus showing the blood ducts.