Menstrual cycle takes place every month for a period of 6-7 days. During these days, a woman may have abnormal cramps along with some other minor problems, such as headaches and stomach harassment. When menstrual blood flows quickly from the body, its color will be red or pink. Sometimes, most of the women may notice black or brown blood during the period and then worry. According to experts, that blood is dark indicates that it slowly flows out of the body.