Yes, the idea that humans have blue blood is a myth.
While veins often appear blue through the skin, the blood inside them is not actually blue. Human blood is always red, although the shade of red varies depending on whether it is oxygen-rich (bright red) or oxygen-poor (dark red). The perceived blue color of veins is an optical illusion caused by the way light scatters and is absorbed by the skin and blood vessels.
Here's a breakdown:
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Oxygenated Blood: Blood that has just passed through the lungs and is carrying oxygen to the body's tissues is a bright red color. This is the blood you'd find in arteries.
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Deoxygenated Blood: After delivering oxygen to the body's tissues, blood returns to the lungs through veins. This blood has less oxygen and is a darker red color. It appears bluish through the skin due to the way light is absorbed and reflected.
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The Illusion: The skin absorbs longer wavelengths of light (reds and yellows) while reflecting shorter wavelengths (blues and purples). Because veins are located beneath the skin, the red blood within them appears bluish to our eyes.
In conclusion, while veins may appear blue, blood itself is always a shade of red, and the notion of "blue blood" in humans is a misconception.
