This is a popular question, so I’m going to steal
some from the last time I answered it.
Blood is actually red all the time, but
different colors of red. When you see blood
outside the body it is usually a dark red. This
blood is from the veins, so it has already dropped
off a lot of its oxygen to cells that needed it.
Sometimes you may cut an artery. This blood is
bright red because it has not yet dropped off its
oxygen. It also spurts out in pulses instead of
oozing like the blood from veins. So even outside
the body, blood can be different colors.
What's the difference between veins and
arteries and why would that affect the color? Why
does arterial blood spurt?
The blood vessels you see at the surface of
your skin are veins. Everyone's skin is slightly
different in color, so the veins can look
different in different people, but blood is
exactly the same color in everyone. It still
doesn't look red. That's because we're seeing the
*walls* of the veins too. When you see lemon- lime
flavored soft drinks in plastic bottles they
usually look green, but when you pour them out,
they're often clear or yellow. It's not the blood
that's bluish; it's the whole vein, including the
walls, just like the soft drinks look green
because they're in colored bottles.
Have you ever seen a totally white rabbit or
mouse? They're called "albinos" because they can't
make pigments (the substances that color our eyes,
skin, and hair). Their veins look red, even though
their blood is the same color as ours. Why is
Thanks for asking,