Our skies are too grey: Where is the colour?

Abstract

The Daylight Illuminant D65, a standardised reference light source in design and research with a colour temperature of 6500 K, is often used to describe the colour of the daylight. However, it represents the colour of an overcast sky, failing to capture the variability and richness of actual daylight, particularly the blue of clear skies. Recent research shows that both sunlight and skylight significantly influence our mood, perception and physiological responses. The colour of daylight is influenced by factors like sun position, weather conditions, as well as geographical location. To address these variations, researchers are collecting worldwide spectral daylight measurements, emphasising the need for localised spectral reference data to appropriately represent daylight in different locations.