...you saw me standing alone...

Blue moon, of course.  But what's the origin of the expression?  There are several explanations.  The "official" definition of a blue moon is the second of two full moons which appear in the same month (it's just happened in August), or the third of four which appear in the same season.  Because the moon's cycle is slightly shorter than a calendar month, this two-in-a-month or four-in-a-season event will only occur every two-and-a-bit years, which is seldom enough for it to be worthy of comment, hence the expression "once in a blue moon" for an unusual event.  But why blue? No-one knows, but there is a 16th century poem poking fun at the Church's insistence that it had all the answers, which includes the line "If they say the moon is blue, we must believe it is true".