4wk old /c bright green mucuousy pooh, about a tbsp. Breastfeed, normally have mustard yellow stool. No temp, baby feeding well. Concern?

Normal. No concerns, baby's stool is normal.
Infant stool. This is of no concern unless it remains green and has foul odor or has blood in it. Infants can have 1-14 stools/day. They are generally loose and yellow ( like gulden's mustard or bird seed). Green reflects level of bile absorption.