This Saturday when you look up at the night sky, to gaze at the stars, make sure to take one good look at the moon, for it's 'once in a blue moon'. October 31, when most of the Christian world will be celebrating halloween, the sky will be engulfed with this phenomenal event that's a rarity. The last blue moon occurred in 2018 while the closest falls on this weekend. Do observe this wondrous phenomenon for you won't see it till 2039.
The term 'Blue Moon' shouldn't be taken literally. As freaky and interesting the idea of a blue coloured moon sounds on Halloween night, it is unrealistic. The colour of the moon is pale and grey, just like always. NASA in a blog post explains that Blue Moon is a fairly infrequent phenomenon involving the appearance of an additional full moon within the same month. There are approximately 29.5 days between full moons, making it unusual for two full moons to fit into a 30 or 31 day long month. Thus, February will never have a blue moon.
The phrase 'once in a blue moon' has been around for more than 400 years. The meaning of the phrase is akin to 'never'. However, it turns out that the moon can appear bluish! NASA said that events such as forest fires and dust storms can give the moon a bluish tint, as it did in 1883 after Volcano Krakatoa erupted. Looks like we should never say never.