What Causes Black or Tarry Stool? What is the cause of recurrent melena stool with multiple telangiectasia and prominent veins in the proximal ascending colon in a 14 year old boy? There are no 50 shades of melena, only one color: Black; and it's a color that smells bad. Otherwise it's not melena or it's derivatives (melenic, melanotic, melenatonic ) Great thread w a Stool Colors and What They Can Tell You Your stool color can carry important clues about digestion, diet, or even disease. Most shades are harmless, but some changes signal the need for