Breastfed newborns generally have 3 or more bowel movements per 24 hours by day 3 or 4. Formula fed infants generally have at least 1 bowel movement per 24 hours. But some infants can have up to 20 per day and still be normal! And normal breastfed newborn stool is extremely loose.
In an adult, this would be called diarrhea, but it is normal for a newborn. Formula fed stool tends to be more pasty. Any color from bright yellow to green to brown is normal. By age 3 to 6 weeks, the frequency of stool decreases (even once a week for a breastfed infant at this age can be normal as long as it is soft and passes easily).