Almost everyone has experienced a bruise on their skin after a bump on a part of their body, and with time, the bruise will become colorful and a little bit bruised. Why does bruise change color?
  It turned out that bruises were formed by rupture and bleeding of capillaries under the skin. When the bruise had just formed, its color came from the blood leaking from the blood vessels, showing a bright red color. After that, the white blood cells rushed over to clean up the mess, and the color of the bruise would change accordingly.
  The dead red blood cells in the bruise are engulfed by macrophages, and the heme in them is broken down. Heme will produce biliverdin under the action of microsomal enzymes. Then, biliverdin will be further metabolized and converted into bilirubin. Bilirubin is a dark green substance, and bilirubin is orange-yellow. After heme is destroyed, the iron ions in it will be released and combine with ferritin to form golden yellow hemosiderin. The color change of bruise is formed under the joint action of these pigment substances.
  Generally speaking, bruises are bright red when they are first formed, then gradually become dark purple with the destruction of heme, and then they will show the blue-green color of biliverdin, and when bruises are about to heal Out of golden yellow with hemosiderin. Therefore, bruises are at different metabolic stages, and the injured area will become colorful.