Dog Vomiting Bright Green. If there’s red color in the vomit, this means that blood is in the stomach, mouth, or esophagus. Dogs can sometimes eat grass when they are outside, and the vomit, in this case, is usually bright green.

A dog who throws up green bile may have gastritis, meaning a stomach inflammation. If your dog is throwing up green material, it's likely either something green that he ate or bile from his stomach. The dog may first develop vomiting, but severe cases can progress to neurologic signs and death.