Light is measured in degrees Kelvin and the colour temperature changes throughout the day. For practical purposes either end of the day has a lower colour temperature and is redder in nature than the middle of the day where the light is hotter and appears bluer without so much of a cast. To show this I have taken pictures in the morning and middle of the day. (The picture above was taken in the middle of the day).

The practical application of this knowledge is that light in the early morning and late evening is often more appealing, warmer and gives images with interesting shadows giving relief to the landscape. You only have to watch the sun rise and set over a mountainous landscape to see this effect and how quickly the landscape can change in front of you. It is essential to read this light and take pictures that capture the best moments.