Stool question

Sorry guys but this is going to be a TMI question.

What do black/dark stools mean, besides possibly being from blood?

A little background from my last week to better help everyone. 

Last week I was very sick and my GI tract was trying to kill me I'm sure of it. For two days I had pure water diahrea, followed by a day of somewhat constipation with small pellet size bowel movements when I went, followed by a day of thin somwhat long movements, followed by two days of some regular sized kinda hard black movements. Now they are still fairly dark and what I call half diahrea/half constipation because they aren't fully solid and I sometimes have to struggle to empty.

 

Purple Kool-Aid or anything with a dark food coloring in it.

Also, Pepto Bismol makes stools black. Harmless side effect. If you've been taking anti-D meds and can connect the black stools to starting to use them, then they may also be the cause of it.

I clearly remember the day I ate a bowl full of fresh blueberries (while I had my temporary colostomy, 9 years ago, waiting for my take down surgery). My stool turned a dark, army green. And kept coming, for over an hour. It was just a good thing I was home. Later my colon doc said to stay away from any berry. I've followed his advice ever since - even now since I tend to live in the bathroom and food goes right through me. I may have 5 total blueberries, but never a bowl full as I used to.

Certain foods or meds can turn the stool very dark colors.