Bile is formed by the liver and secreted into the intestine for fat digestion by the gall bladder.
It is composed of bile salts, cholesterol, and bilirubin.
A person might throw up bile if they are vomiting from an empty stomach or if food poisoning has happened.
If a person is vomiting bile multiple times, it might be due to bile reflux which is caused due to the entry of bile from the liver into the stomach and esophagus.
It is not of serious concern and can be treated easily within a short duration with rest and hydration.