A blue moon is a second full moon that appears in the same month. It's the first time a Halloween full moon has appeared for all time zones since 1944, according to Farmers' Almanac. The last time a Halloween full moon appeared was for the Central and Pacific time zones in 2001. The "once in a blue moon" phenomenon does not necessarily mean the moon will look blue on Halloween. While the dark blue tone of an evening sky can affect the coloring we see, the moon will most likely not appear blue at all. Whatever the moon's color, hopefully you can catch a glimpse of the beautiful full moon on Halloween!