It is normal for brown discharge to appear on the first day of menstruation. Due to the withdrawal of estrogen and progesterone, the endometrium is not supported by hormones and will become necrotic and shed, when there is hormonal withdrawal, the endometrium is shed less and the bleeding is also less, sometimes it is brown discharge. The bleeding will be more in 2-3 days after menstruation, when the vaginal acidity will decrease and the bleeding will be dark red or bright red, these are normal phenomena not to worry.