Coloured skies

Red sky at night sailor’s delight, red sky in the morning sailor’s warning… but what makes the sky turn from red to blue and back again? It’s surprising how often we are asked this very question.

The sky changes from blue during the day to often red or orange as the sun rises and sets. This is because of the atmosphere surrounding the earth. It is made up of billions of particles that are so small they can’t be seen with a human eye. Light hits the particles as it travels from the sun to the earth, bouncing off them and scattering around.

During sunrises and sunsets the sun is low in the sky which means it needs to travel through a thicker layer of the atmosphere. This means the sunlight is bounced off more particles so most of the blue and violet light is scattered leaving only the orange and red light to colour the sunrise or sunset.

During the middle of the day the sun is higher in the sky. Less sunlight is scattered leaving more blue light to travel through the atmosphere so we can see it.

All of which leads to a second question: How do you match the blue of the sky? The exact blue is completely variable depending on a whole host of factors including where you are and the time of the year/day. The best idea is to either take a photo of the sky and get it colour matched or take your handy Resene Multi-finish palette colour set outside and match the desired sky colour up to a Resene colour chip to ensure you are getting a sky blue that matches your expectations.