This may happen when the force of regurgitation causes tiny tears in the blood vessels lining the esophagus. Your baby's vomit may also be tinged with red if he has swallowed blood from a cut in his mouth or a nosebleed within the last six hours. Call your doctor if your baby continues to have blood in his vomit or if the amount is increasing. The blood could be bright red, or it may resemble dark coffee grounds. The doctor will probably want to see a sample of the vomit if it contains blood or bile, so distasteful as it is, you should try to save some.
Green bile can indicate that the intestines are blocked, a condition that needs immediate attention.
Violent, persistent vomiting within half an hour of eating. This may be due to pyloric stenosis , a rare condition that is most likely to begin when your baby is a few weeks old but could show up any time before he reaches 4 or 5 months. Babies with pyloric stenosis vomit when a muscle controlling the valve leading from the stomach into the intestines has thickened so much that it won't open up enough to let food through. The problem is easy to fix with minor surgery, but does require immediate medical attention. Contact your pediatrician as soon as possible.