Does a blue moon refer to a blue-colored moon?

Answer:
No, it is the name given to a second full moon occurring in the same calendar month. (This does not happen often)

Some sources indicate that the original "blue moon" was the 13th calendar-year full moon, which occurs because the calendar year has 11 more days than the 12 lunar months. Every two or three years there is a 13th full moon.
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