What color is deoxygenated blood?

Answer 1

Blood is never blue. It does not give up its hemoglobin, it gives up (part of) its oxygen. If you get blood taken, it's from a vein, and it's not blue. It never meets oxygen during the transfer. Deoxygenated blood is most certainly NOT blue, but a darker red. Veins are made blue by distortion of light by your skin which prefers to take in the red light spectrum and turn away blue. The vein itself is actually white or cream in colour. Many people think blood is blue because of textbooks making diagrams blue, so as to not confuse readers on where the veins are located.

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To expand on the above answer... Oxygenated blood is a bright red and deoxygenated blood is a darker red. This is because of the molecular shape/electron configuration of oxyhaemoglobin making it absorb a specific part of the visible spectrum. Deoxyhaemoglobin differs slightly in its shape due to the lack of oxygen.

Specifically, hemoglobin contains a heme group. This heme group consists of a single iron atom surrounded by a porphyrin ring. The ring absorbs color from the visible spectrum because of its high number of conjugated double bonds. The iron atom serves as a chromophore; when bonded with oxygen it changes the wavelength of absorption---giving the blood its lighter red color. Without oxygen, the color changes.

I've heard there may be a slight blueish tinge to deoxygenated blood but if you see it, it is decidedly dark red.

Veins appear blue when looking through the skin because the tissues of the bodily more readily absorb red. Blue is unable to pass through the opaque walls of veins and is reflected back to the eyes. Also, because of the way the brain processes color the difference between pinkish skin and the blue tinge is exaggerated. However the capillaries will appear red because they are not 0.5mm below the skin, so the subcutaneous tissue has not absorbed as much light as it would for a deeper vessel.

I may be slightly off on a couple particulars but that's the gist of it.

Answer 2

It's red, but not as red as oxygenated blood.