Bruising occurs when a blunt force trauma causes damage to the capillaries beneath the skin. The damage allows blood to escape into the interstitial tissues. This leads to the characteristic color changes associated with bruises, which are a result of the breakdown of hemoglobin from red blood cells. Initially, the bruise appears red or purple, then turns blue or dark purple, and eventually becomes green, yellow, or brown as the hemoglobin is broken down and reabsorbed.
