The last Blue Moon was seen in 2020. Unlike its name, it is not blue in colour.
The moniker came about due to the Blue Moon being the second full moon in a calendar month – a rare sighting that happens every two to three years.
However, there are instances where the moon has appeared to be blue, due to water droplets in the air, certain types of clouds or particles thrown into the atmosphere by natural catastrophes such as volcanic ash and smoke.
This was seen during the 1883 volcanic eruption of Krakatoa in Indonesia. Back then, ash particles in the air scattered red light and acted as a blue filter, resulting in the moon taking on a blue appearance.