Why the heart is red?

The color of the heart is actually more maroon than red. This coloration comes from the oxygenation state of the blood flowing through it. The bright red blood pumped out by the heart to the rest of the body is not actually bright red within the heart. The blood in the heart and coronary arteries is actually closer to a deep, wine red color, while the blood in the lungs and large veins is more purple. The difference in color is because of the oxygen carried by the blood. When blood is carrying oxygen, it appears bright red, and when it is not carrying oxygen, it appears purple.