The color of period blood can vary from bright red to dark brown or even black, and these changes are usually a natural part ...

Bright red period blood is common at the start of your period and indicates blood has passed through your vagina quickly. Orange, gray, or green tinges in period blood can be signs of an STI or other ...

Dr. James Faber is professor of cell biology and physiology at the UNC School of Medicine. Here he explains how principles of chemistry and physiology combine to create the color scheme of blood.