that's about how I am. especially if I have clotting. The clots always look black, but they aren't. Old blood (what usually comes out towards the end of the period) is brown and if there is alot, it's very dark brown and can look nearly black.

It seems for me, if I have a three days period I start it with a vengance and I bleed heavily very dark red and then it suddenly just ends.

If it is a longer period, then it is very similar to what you describe your cycle as.