Think due to some kind of cosmic dust or something I read somewhere this blue moon will actually be tinged blue too (except during the eclipse, one assumes, when it will have a red tinge). That page has other reasons the moon has been visibly blue.
The rarity of a visiby blue moon (accounting for "once in a blue moon" usage) added to the relative rarity of an extra moon in a calendar month, is a similarity that possibly accounts for the naming mistake made in 1946 related on that page. The mistake changed old usages of the term blue moon for the modern one used today. This is the usage that states the extra moon in a month is a blue moon.