I had an old MB radiator recored too. The green in my case was due to a definite leak & resulted from a reaction with the underlying brass, not green antifreeze, much as seawater or weather exposure results in a green patina on this metal. Mine was painted by the shop & continues to look OK. I have been warned, however, not to apply too thick a paint layer or too many layers as this will interfere w/ heat transfer. -JP-