It was the second full moon of the month, and therefore called a "blue moon", but was it blue??? Not so much...
In certain circumstances, the moon can appear to be blue, for example, when there is ash in the atmosphere from forest fires or volcanic eruptions. We also use the phrase to describe something occurring rarely ("once in a blue moon") or to describe a second full moon in one month, an extra full moon in one quarter of the calendar year or a season. There is however, no astronomy or folklore to support the use of an expression which seems to have found its way into modern parlance, thanks at least in part to an article published by a backyard astronomer in Sky and Telescope in the 1940s.
Whatever one calls it, this backyard astronomer thought last night's full moon was just grand, blue or not.
Merry Lammas everyone, and happy August!