The blood of a human being is supposed to be red. However, the quality of the red factor differs depending on the specific person. Some people have a blood that is slightly darker than the normal red color.
Wrong. Blood is never blue. Ever. Period. (And, this is an excellent example of why you should never ingest information from Yahoo Answers uncritically.) The bright red color of arterial blood stems from a complex that's formed between hemoglobin, iron, and molecular oxygen. This complex mainly absorbs higher energy (shorter wavelength) blue and green light, leaving behind primarily just red wavelengths for our eyes to detect. However, even when blood is largely depleted of oxygen, it is never blue: it's more of a deep maroon color. And, although I have not participated in a surgery myself, those who have (including my girlfriend, a veterinary student) assure me that in surgery, veins within the body do not appear blue either. So, not only is blood not blue, veins on their own aren't either. "Blue veins", then, are a phenomenon unique to the skin.
Blood is always red. You know when doctors take your blood from the tube...there is no air in that tube. And we were just talking about this the other day too. Your veins are blue but not your blood. True facts.
The Vein Is A Blood Vessel That Carries Blood From The Capillaries Toward The Heart And Are Visibly Blue. The Blood Inside Of These Vessels Are Contained Red. The Only Red Visible Internal Stream Is The Artery. Therefore, Blood Is Red. Although It Is Not Externally. When The The Skin Is Cut, The Reason Why Our Blood Is Red Is Because A Very Small Piece (Varied) Is Cut Open Therefore The Blood Leaks.
I'm actually getting pissed about all these people acting like they know something just because they heard it from someone else. Blood doesn't turn blue when it hits oxygen... The purpose of blood is to transport oxygen!!! When O2 goes from the alveoli in the lungs into the pulmonary veins it is now bright red because it's oxygenated. After delivering the O2 to whichever tissues or organs via the systemic arterial circulation it becomes a darker red and heads back to the right side of the heart via the venous system and back to the lungs for more OXYGEN!! It's an amazing process that keeps on going until the end of our life.
Good grief, blue?... Arterial (oxygenated) blood is bright red, venous (oxygen depleted) blood is a darker shade of red. There are a few medical conditions that could change the colour of blood such as poisoning with certain metals, but for all intents and purposes, your blood is red.