During the first few days of life, your baby will pass meconium, the thick, black or dark
green substance that was in his intestines before he was born. Once the
meconium has passed, the bowel movements of a formula-fed baby are typically yellow, tan, brown, or green. As long as there isn't blood in the stool, any color is normal.
A formula-fed baby's stool is a little bit firmer than a breastfed baby's, about the consistency of peanut butter.