When bleeding why does your blood have two distinct colorations?

Blood has one color when it's in your veins and another when it's outside of your body. Deoxygenated blood is carried through the body in the veins, and it has a darker red color. Oxygenated blood is carried through the arteries, and it has a bright red color.

When you cut yourself, the blood that comes out of the vein is dark red. Then, you'll notice the clot of blood will begin to form a scab at the wound site, and the color will change from red to brown or black.