I have drawn blood multiple times from a pulmonary artery catheter (blood coming from the heart, right before it hits the lungs, ) when blood has the least amount of oxygen as is possible and it is dark red. No hint of blue, just dark red.
If you are thinking "Hey! You said “artery”. Just think of arterial and venous as directions of travel, artery means away from the heart and venous means back to the heart. The pulmonary artery is deoxygenated blood and the pulmonary vein is oxygenated blood that is returning to the heart so that the heart can send it ‘away’ with more force so that it can reach the tips of your toes. 
Blood from an artery is much brighter. When someone has very bad lung problems the venous blood will be so dark as to appear brownish-red but still not blue.
I think zombie blood might be blue.
Have these people that think venous blood is blue never cut themselves?
They’ve just got crazy luck and keep nicking arteries.
The theory goes that the moment the blood touches the air it absorbs oxygen and becoems red again. But I’m sure they’ve all ahd blood drawn - into a vacuum tube as stated above.
I used to think it was blue (because of the diagrams in my biology textbook). And yes, I occasionally pricked my finger.
But the blood is exposed to the air, and can take on oxygen. It turns red in an instant, so we never bleed blue…
… Is what I used to think.
"Because it’s always taken from an artery. "
You donate arterial blood? Damn, that’s hardcore!
Anyway, the blue blood argument is still popular because some people see the color of deoxygenated blood as “purple.” It’s really just a darker red than arterial blood, but it’s not exactly wrong, especially in comparison to the bright vibrant obvious red of arterial blood.
There’s a reason all those medical textbooks showing pictures of the cardiovascular system typically use red and blue coloring to indicate arteries and veins. In reality the color difference isn’t that extreme, but the pictures aren’t just making up “blue” for absolutely no reason. Blue (purple really) is just a liiiiiiittle bit down the spectrum from where venous blood actually is, and since we all know that color definition is subjective and arbitrary…
…anyway, the correct answer is “it’s complicated.”
ETA a very relevant picture
When I used to sell my plasma in college, it was very easy to observe this phenomenon. They separate your red blood cells from your plasma, re-injecting the RBCs and keeping the plasma (because plasma is regenerated many times faster than RBCs, you could donate a much higher volume of plasma than whole blood. I gave them 880 ml twice a week). If you ate healthy for 24 hours beforehand your plasma would be nice and clear, but if you loaded up on greasy/fatty foods it would be noticeably cloudy.
I’ve no idea, to tell the truth. Does donated blood come from veins or arteries? I never thought about it.
Does it make a difference?
Blood nicely drains out of a vein stick. It might shoot across the room with an arterial stick, being under pressure.
aside from me in US
::What’s a sprog?::
::I didn’t get your “::removes cap…”::
/aside for me in US
offspring (a very … um… casual term, to say the least)
I think there was a certain amount of sarcasm there…