During the first three or so days after your baby is born, he will pass black, tarry stools (meconium). This is normal. The stools will slowly become lighter in color, less sticky and become more liquid.
If you see blood in your baby's stools, call your baby's health care provider
If you breastfeed your baby, the stools will be green-yellow to mustard-yellow, seedy and liquid. If you are only breastfeeding (your baby receives no supplemental feedings), frequent and liquid stools are not a concern or a sign of diarrhea.
If you formula feed your baby, the stools will be darker, more solid and have a stronger smell. Your baby will have fewer stools, and they will be larger than those of a breastfed baby.