How can hemoglobin influence skin color?

Hemoglobin is a complex protein carried by erythrocytes (red blood cells). Hemoglobin transports oxygen from the respiratory organ(s) to the cells, and carbon dioxide from the cells to the respiratory organ(s). Because hemoglobin contains iron, and iron, when combined with oxygen, demonstrates a characteristic red color, hemoglobin causes blood to appear red (oxygenated blood is bright red, deoxygenated blood is a dark red, sometimes with a bluish hue). Because hemoglobin appears red, it can cause skin color to appear reddish or flushed/blushed (erythematic). As it breaks down, hemoglobin loses its reddish color and may instead appear blue, yellow, brown, purple, or even black. This is why bruises initially appear red, but then may change colors.