First day of period is dark colour?

Have any woman experienced in having dark colour of period during first day of period? I don't know why and how it gets there.

Some friends ask me about this but I don't know how to tell them. I know some friends that do not like to see doctor so they just ask around to see if anyone gets the answer. Being a woman has so much to go through than men.

I found this article about menstrual period cramps to share with everyone.