The colour of light

Sunlight is our natural source of light.  During the middle of the say it appears colourless - we refer to this as white light.  This is what we regard as normal light. 


Light becomes colour when a part of the spectrum is missing.  Daylight normally has two colour directions. On a good clear day, when the sun is lower in the sky it becomes yellow, then orange and if you have a good sunset red by the time it reaches the horizon.


The reason this happens is because all the particles in the atmosphere scatter some of the light and there is more atmosphere between us and the sun at sunset.  The blue wavelengths have been scattered leaving the yellow/orange colours to come through. 


On a sunny day in the shade the orange/yellow is scattered making the light coming from the sky blue.


The colours of daylight can be seen on a scale that runs from red to orange to straw-coloured to white and then blue.  This is called the colour temperature scale. The temperature is measured in degrees Kelvin.
Generally the cooler the Kelvin temperature the warmer the colour and the warmer the temperature the cooler the light.