Hi,
@MsBea, that's a very good question and one I have often thought about, but never taken it any further, until now.
I googled the colour of blood and these came up :-
Does the color of your blood mean anything?
The level or amount of oxygen
in the
blood determines the hue of red. As
blood leaves the heart and is oxygen-rich, it is bright red. When the
blood returns to the heart, it has less oxygen. It is still red but will be darker.10 Apr 2018
The color of human
blood ranges
from bright red when oxygenated to a
darker red when deoxygenated. It owes its color to hemoglobin, to which oxygen binds. Deoxygenated
blood is
darker due to
the difference
in shape of
the red
blood cell when hemoglobin binds to it (oxygenated) verses does not bind to it (deoxygenated).