We’ve long known that soft candle light generally triggers a gentler mood, and grey skies can make us more gloomy. Some people tend to be depressed in the winter, when the sun sets early.

Researchers at the German Fraunhofer Institute are now testing what kind of moods are associated with colored lighting. They found out that red light has more of a relaxing effect that will make us want to lie down or go to sleep. It’s the same red tones that appear on the sky at sunset. For our hunter and gatherer ancestors who lived mostly outdoors this was the signal to retire into a sheltered space.

In contrast, blueish light will wake us up, make us more alive and increases the drive to move. Yellow is said to increase concentration.

Research concludes that when workers in an office were forced to work in a space without windows, their levels of tiredness were much higher than of those who were exposed to daylight.