I have never heard of a planetary 'occultation' by the Moon being referred to as a 'Blue Moon'. I think that whoever told you this got their terms confused! Blue Moon, in the literature I have come across, either refers to the double Full Moon in a month, or a rare atmospheric phenomenon which some observers have seen. More information can be found in the May 1999 issue of Sky and Telescope magazine.
Copyright 1997 Dr. Sten Odenwald
Return to Ask the Astronomer.