My friend that just had a colonscopy was found to have a black colored colon caused by overuse of laxatives. In her case she has been using a colon cleanse everyday due to constipation. I was not aware of this. It is not been proven to be of harm long term but she was told to take Miralax from now on. It is called Melanosis Coli. Wonder if anyone else has heard of this. She has just recently started to have IBS like problems which is why they did the colonscopy.