Women’s labia will be black mainly due to three reasons: First, individual differences, women’s labia and women’s body skin color is relatively dark, darker women’s labia will be relatively black, lighter women’s labia color will be relatively light, which is caused by individual differences. Second, after female sexual maturity due to estrogen levels increase, estrogen will lead to female pigmentation in the reproductive organs pigmentation, which is the performance of female sexual maturity, women in the sexual maturity of the vulva and vagina color will become black. Thirdly, the color of labia will be further deepened after pregnancy, because the level of estrogen and progesterone will rise abruptly after pregnancy, and the rising hormone level will further aggravate the pigmentation of reproductive tract, and the color of reproductive tract will be further deepened and darkened.