Revealed: Secret behind the changing colours of moon  

At night, when you look up at the sky, what colour is the moon? Is it white, peach, pink, blue or grey? Well, all these are the more familiar colours of the moon but have you seen an orange moon? How about a purple one? The moon does put up a show, different every time in shape, colour and beauty. But how does it do that? Let us find out how the moon changes colour like a chameleon.  

Earth’s atmosphere is the cause 
Moon’s actual colour is grey and it does not have any light of its own; it reflects light from the sun. So, if we were anywhere outside Earth, this celestial body would appear as brown-tinged grey. However, its colour can vary substantially when we see it from Earth depending upon where the moon is in orbit around the Earth. The perceived colour of the moon also changes according to the angle at which sunlight hits the moon.  

Blue Moon 
Heard the saying “Once in a blue moon”? What does the Blue Moon mean here? The phrase implies that something is rare like a blue moon. So what is Blue Moon all about? How does it turn blue in colour? This happens when there is an enormous amount of dust and smoke in the air which make the moon appear blue in the night sky. You would be able to see this kind of atmosphere created by wild forest fires or major volcanic eruptions. The last time the moon turned blue was due to the eruption of Krakatoa in Indonesia, in 1883 which tinged the moon blue for a long time. 

Also, it is a term attributed to the 13th full moon. However, it has nothing to do with the colour of the moon. One lunar cycle or one full moon takes 29.5 days to complete, meaning 354 days total for 12 full cycles. This falls few days short of the normal 365 or 366 days in a calendar year. And therefore, roughly after every two and a half years, a 13th full moon is observed which is named as a ‘Blue Moon’ because of its rarity.  

Red Moon 
Once the moon has reached a total eclipse in the full moon phase, Earth is positioned precisely between the sun and the moon. The moon completely hides the solar surface and thereby cuts off all direct rays of sunlight from the observer on Earth. This makes it  appear red, thanks to the residual sunlight from Earth’s atmosphere which is scattered towards it. This is what gives away a reddish tinge. This phenomenon is also known as “Blood Moon“.  

Yellow Moon 
June’s full moon is known by many names: Strawberry Moon, Honey Moon and Yellow Moon, thanks to the yellow colour. The sun is highest in the sky in the Northern Hemisphere around June and therefore, the moon at that time is lowest in the sky. We see it through a thick atmosphere which turns it yellow, just like the setting sun. But why is it called Strawberry Moon? That has nothing to do with its colour. The native American Algonquin tribes named it to mark the ripening or harvesting of strawberries in this month. 

Orange Moon 
Again, the moon seems to be orange in colour when it is very low on the horizon. This is because the light emitted by sun has to pass through much more of Earth’s atmosphere to reach the moon and shorter blue wavelengths of light are scattered more, leaving the longer red wavelengths to reach the moon. This is what makes it appear reddish or orange.