When you first get a bruise, its kind of reddish as the blood appears under the skin. Within 1 or 2 days, the hemoglobin (an iron-containing substance that carries oxygen) in the blood changes and your bruise turns bluish-purple or even blackish. After 5 to 10 days, the bruise turns greenish or yellowish.

Is it bad if a bruise is black?

Occasional black and blue marks from bruises are a normal occurrence. Bruises can be uncomfortable, but they usually heal on their own unless theyre associated with a medical condition. See your healthcare provider if a bruise doesnt improve or resolve within three weeks.