Hello! Thank you for the query. Black vomiting is caused by bleeding to the stomach. However its hard to tell about the source of bleeding from my point. Most common sources of such bleeding are esophageal varices (caused by liver cirrhosis), peptic ulcer or even stomach cancer. Bleeding from lungs and swallowing the blood can also cause such vomits. Swollen colon is probably a situation described by an ultrasound. Such swelling can be an inflammation or a cancer indeed. Abdominal CT and colonoscopy should be considered (in case of diverticulitis, colonoscopy can cause perforation). Stomach and esophagus should be diagnosed with gastroscopy. So you can ask a doctor about mentioned tests. Hope this will help. Regards.