why do people think blood is blue?

how about you see a doctor rather than go on yahoo answers

I find this funny as i recently found this out, but when scientists started studying the body, they used blue for "oxygen poor" or

deoxygenated blood, and red for "oxygen rich" or oxygenated blood. When the public saw this, many assumed that the deoxygenated blood is blue and that blue blood is real. As you know now, this was a huge misunderstanding, as deoxygenated blood is a really dark red and oxygenated blood is a bright red. As for veins being blue, I do not know and will most likely try to find out and give you an answer. But for now, know that there is no such thing as blue blood or blue blood cells. Sorry for typing something so long.

What you see in varicose veins and the veins in your forearms on the inner side show blue.

o If you look at your wrist, the blood vessels you can see look kind of bluish.

o Illustrations in science textbooks frequently use blue in the illustration for veins and red for arteries.

o The fetal pig you dissected in high school had blue rubbery stuff injected into the veins and red rubbery stuff injected into the arteries.

o Tradition. Their grown-ups told them so when they were kids.

There are a number of reasons. Some people believed, incorrectly, that blood in veins, at least, was blue, because it was de-oxygenated, but when exposed to air it turned red. De-oxygenated blood in the systemic veins is not blue but a dark red.

Another reason is that when you look at your skin and see superficial veins they look blue. Of course what you are seeing is not the colour of blood but the wavelengths of light reflected from the various structures there such as skin, subcutaneous tissue, vein walls, etc. This seemed to confirm for some that venous blood is blue.

A third reason that compounds these mistakes is the colour used for blood vessels on diagrams showing the blood circulatory system. Conventionally, arteries are coloured red. To distinguish veins from arteries a different colour is used and that is blue.

As others have said, due to veins looking blue under white skin, but I think historically it was a popular misconception and they thought air turned blood red because they didn't know about oxygen. There was/is also an English expression "blue blooded" which came to mean "of noble birth", effectively because white people who don't work outside have very pale skin which shows the blue appearance of veins. Thus the British white nobles, who didn't do manual labor, looked particularly blue blooded.

Because veins are blue, and as kids, people think and spread the idea: "hey look, these veins are blue? The blood goin through em must be blue!", because they have no reason to think otherwise unless taught.

Then that information is spread to others and... yeah.

That's where that stems from, probably. Just innocent ignorance.