The irony of the subtitle is that this is the most often read portion in the entire Torah, read every new moon (16-18 days a year), as well as every day of all of the festivals (25 days in the Diaspora, 22 in Israel), the High Holidays (3 days a year), as well as this week four times on the market days. You might be reading this portion for as many times as there are Shabbatot in the year.
So why the blue moon? Well, the moon is sad. The reason for this can be seen in a midrash based on an anomaly in one of the readings in Pinchas. As mentioned before, this parasha is read on all of the festive days of the year besides Purim and Chanukkah and the reading contains the sacrifices of the day. One of the final offerings listed on each and every occasion is a goat for a sin offering. This is pretty uniform except for the reading for Rosh Chodesh in which God's name is added. Commentators (at least according to one of my college professors) have said that God asks us to sacrifice a chatat offering from him to the moon. Why? Because God ordained the laws of nature, including that the moon is diminished from the sun, and yet, once a month the sun trespasses on the territory of the moon, causing it to temporarily disappear. To appease the moon, God orders a sin offering on His behalf to the moon. I know it sounds pagan.
The Moon: Don't trespass! Beware of Dog! Don't Tread on Me!
Shabbat Shalom, and stay of my danged lawn...