Your baby's very first poop should actually be a tarry black (maybe a little greenish) color. This gooey stuff is called meconium, and you shouldn’t see it after baby is three days old. (If baby is still passing meconium on day four or five, get help ASAP. This could mean he isn't drinking enough milk.) After that, for the most part, moms find that exclusively breastfed babies tend to have soft, Dijon-mustard-yellow poops, with little clumps that look kind of like seeds.
But don't worry — some other hues are just fine too. Green poops are usually okay, as long as baby is content and gaining weight. Orange poops are also normal, as are other shades of yellow or brown, or combos of orange, yellow, mustard, brown, and green. If baby has black poop well after the days of meconium, there could be blood in his digestive track. In this case, call the pediatrician to check things out. Also call the doc if you see blood in baby's poop (it could have come from the colon or anus) or if baby's poop is chalky white (which could mean there is no bile in the liver to digest food).