The first day of menstruation for women is black for the following reasons: the first case, may be due to the period of endometrial exfoliation less, the uterine cavity of the accumulation of blood less, flow to the vulva will appear black menstruation, in the period of 2-3 days after the flow of blood, menstrual blood will turn dark red. In the second case, it may also be caused by cold or mood swings on the first day of menstruation, which may lead to stagnation of blood. Therefore, if a woman has black color on the first day of menstruation, she can also take Zhuangyao Wan or Blood Mansions and Stasis Capsules or Yimu Cao Granules orally if necessary, which will help to smooth the flow of menstrual blood and change the color from black to dark red.