Question

why do veins look blue​

Answer 1

The veins themselves are not blue, but are mostly colorless. It is the blood in the veins that gives them color. Furthermore, the blood in human veins is also not blue. Blood is always red. Blood that has been oxygenated (mostly flowing through the arteries) is bright red and blood that has lost its oxygen (mostly flowing through the veins) is dark red. Anyone who has donated blood or had their blood drawn by a nurse can attest that deoxygenated blood is dark red and not blue. Skin scatters a lot of the red portion of white light before it can reflect off the blood, leaving the blue light to reflect off the blood and back to our eyes. It is a similar effect to how the white sun appears red at sunset due to the blue colors being scattered away by the atmosphere.

$\huge\underline\color{red}Samriddhi♡$

Answer 2

this is why the veins look blue in colour