So that’s me about two weeks ago after an unfortunate water tubing incident.  As I was tubing (see below to see what tubing is) I was propelled forward and the rope caught my arm.  This hurt quite a bit and left a nice bruise on my left arm which lasted for about a week.  As you know though, bruises change color and eventually leave you with a spectrum of colors including red, orange, yellow, and more.  Why does this happen?

First what causes a bruise?  

A bruise is simply a ruptured capillary (very small blood vessel) just under the skin.  When these capillaries break, they release blood which pools under the skin.

Why do bruises change color?

Bruises look red initially because blood is red.  They start to change color as the blood breaks down.  Have a look at the video below for a little more detail.