It's always interesting to have one's beliefs paddled over the head by science.
Today I learned that our blood is not blue, even when deoxygenated [via, via]. Who'd'a thunk?!?
In short, it turns out that our venous blood is actually deep maroon... ie, not much different from arterial blood. When vessels are close to the surface of our skin, we see the red. ...Which is why pale folk like me look vaguely pink. But as the vessels get deeper (to about .5 mm), some measure of absorbing and reflecting of light takes place, and you end up with a purple color. Thus, when compared to the pink of your skin, our eyes interpret that purple as blue.
Whacky! ...And humbling. There are still too many urban myths that I believe, even if I have become increasingly skeptical over the years.