Why Bruises Change Color Over Days

Day one, it's an angry red-purple. By the end of the week, it's drifted through green and settled into a dull yellow before finally fading out. A bruise isn't just healing quietly under the skin — it's running a visible chemistry experiment the whole time.

What a bruise actually is

A bruise (contusion) forms when an impact ruptures small blood vessels under the skin without breaking the skin itself, letting blood leak into the surrounding tissue. That trapped blood, not the impact itself, is what you're actually seeing change color over the following days — the bruise's color is a direct readout of what's happening chemically to that pool of blood as your body breaks it down and clears it away.

Red and purple: the freshest stage

In the first day or two, the color comes straight from hemoglobin, the oxygen-carrying protein in red blood cells, sitting in the tissue essentially unchanged. Fresh trapped blood reads as red to deep purple or almost black depending on how much pooled and how deep it is under the skin.

Green: biliverdin takes over

As immune cells called macrophages arrive to clear the trapped blood, they break hemoglobin down in stages. One of the first breakdown products is biliverdin, a green-tinted pigment — the same compound responsible for the green color in some bruises around days 5-7, and notably the same core pathway your body uses to break down blood anywhere it needs recycling, not just bruises.

Yellow, then gone: bilirubin's turn

Biliverdin itself gets further broken down into bilirubin, a yellow-tinted pigment (the same compound responsible for the yellow tint in some other contexts, like jaundice, when it builds up faster than the liver can clear it). This yellow stage typically shows up in the final days of a bruise's visible life, as the last of the pigment gets cleared out of the tissue and reabsorbed.

The whole red-to-purple-to-green-to-yellow arc, usually spanning one to two weeks, isn't decoration — it's a literal timeline of your immune system dismantling and recycling a small pool of trapped blood, one breakdown product at a time.