Blood gets its color from hemoglobin, the protein in your red blood cells that carries oxygen throughout your body. When hemoglobin binds with oxygen, it turns bright red.

Without oxygen connected, blood is a darker red color. Carbon monoxide, a potentially deadly gas, can also bind to heme, with a bond around 200 times stronger than that of oxygen.

All blood in the human body is red in color. It is untrue that deoxygenated blood is blue. Human blood contains hemoglobin, which is a complex protein molecule in red blood cells. Hemoglobin ...

So, blood has different variations of red, but there is never a time when human blood is blue. You've likely witnessed this if you've had blood drawn: A needle slides into a blue- or green-looking ...