Blood that appears black on the first day of a woman’s period is usually a normal manifestation. Because the endometrial lining of the uterus is less exfoliated on the first day of a woman’s period, the amount of menstrual flow is less, and the small amount may be stagnant and oxidized in the vagina, and will be seen as black blood when it is discharged from the vagina. Some women may have coffee-colored or brown menstrual blood, which is usually normal and can usually be treated without special treatment. Some women may experience black blood a few days after their period is about to clear, which is also normal.