The roses are Red. Violets are blue. And so are the arteries and veins, respectively, they are red and blue. Technically, both are red only with different hues.

In all humans and most hemoglobin-dependent animals, the arteries should appear red. Well, it really depends on which arteries you are looking at. If you’re talking about the pulmonary artery that carries deoxygenated blood from the heart to the lungs, then that artery is dark red. But if you are talking about the systemic arteries that carry oxygen-rich blood throughout the body, then it would appear bright red. In contrast, veins containing deoxygenated blood are dark red in color, although they appear purplish or bluish through impermeable skin.

The color of the veins is usually dark red due to the lack of oxygen content. However, it appears bluish or purple due to the way light is absorbed, reflected, and bounced off to the naked eye. Based on a study carried out, few factors that affect the appearance of the veins are the dispersion and absorption characteristics of the skin at different wavelengths, the oxygenation state of the blood that affects its absorption properties, the diameter and the vessel depth, and the visual perception process.

The higher the levels of oxygen bound to hemoglobin in the arterial blood, the brighter the red color will be. So why do you sometimes see dark red blood in blood bags during blood drives? Does it mean they are donating unhealthy blood with low hemoglobin or low oxygen? The answer points to how light is absorbed and reflected to the naked eye and the light-absorbing properties of blood.

If you can see on an ultrasound report the carotid artery, which is the blood vessel that carries oxygen-filled blood to the head, neck, and brain, it will appear bright red. However, if you can see a carotid artery through the dull skin on your neck, it will eventually appear bluish in color.

Since then, there has been a huge misconception about what arteries and veins look like mainly because the veins that you see regularly near the surface of your skin actually look blue to your eyes. Also, in most textbooks used in school, two colors are used to represent the arteries and veins that make up the circulatory system: red and blue. However, this is for illustration purposes only to help students distinguish an artery from a vein. The list of roots of misconceptions could be very helpful. The good news is that at the end of this day you already know what the color of your arteries and veins really is.

So your arteries and veins are red or blue.