My son is 10 weeks old, what would cause his bowel movements to be grey in color? Hes formula fed and no recent diet changes.

Digestion changes. Off color stools is not uncommon in formula fed infants. The whole system is getting used to being on line. Generally the only colors to be concerned about are black as tar, red or white. http://www.webmd.com/parenting/baby/diapering-a-baby-13/baby-bowel-movements.