Take a picture of your shutters. Shoot from a close distance with a digital camera so you have an accurate depiction of what your shutters look like. Get multiple photos to provide a better idea of the actual color. This is simpler than trying to remove a shutter or break off a piece for analysis.
Take the photos to a hardware or paint store and show the employees so they can locate the appropriate paint.
Compare the pictures to a paint color chart at the store to get the closest and most specific color possible for the shutters.