It is quite common for a baby's stool to change color based on their diet. Foods like dates and ragi (finger millet) are known to cause dark, sometimes blackish, stools. Additionally, iron drops can lead to a similar color change. As long as the stool is well-formed, the frequency is normal, and your baby is not exhibiting other symptoms like crying, mucus, or fever, there is typically no cause for alarm. If you remain concerned, track the symptoms and mention it to your pediatrician at your next visit.