What Causes Dark Colored Stools?

Hi, Bought a juicer recently, and Saturday (I think) I had a large glas (12 oz?) of fresh apple juice, and about 8 oz of carrot + apple on Sunday. Yesterday, (Tuesday), my bowel movements produced a very dark colored stool, both morning and evening. I also started to feel like diarrhea was on its way. Today another dark stool in the morning, and a very loose, watery dark diarrhea movement around 3pm. The stool this morning was smaller than Tuesday s, and it does feel like things are moving through , but still I couldn t help but be shocked, never having seen such a dark color before. There was no blood visible, and I did retrieve a small amount of the regularly formed stool. The smell is not bad, almost sweet actually....suggestions?