Stool colour may vary among babies on the same formula. In addition, the colour, number, and consistency of the stools of one baby may vary from time to time. Some mothers report that their babies have yellow or brown stools while other mothers say their babies have green stools. There is a normal tendency for babies on iron-fortified formulas to have more green stools. A baby’s stool colour will often change with a change in formula, or with the addition of new foods or medications.