It's been understood for many years that our bodies respond to ambient light levels, adjusting our internal clocks accordingly.
Bright environments simulate daytime, darker environments simulate night, and we can be subconsciously tricked into feeling like it's a different time of day than it really is. But research tells us that not only the brightness, but the colour of light also plays a role in telling us the time of day.
A study released last year, Telling the time by colour, performed at the University of Manchester has shown changes in electrical activity in mice that were exposed to visual stimuli. Specifically, their bodies were more sensitive in color changes between blue and yellow wavelengths, than they were to changes in brightness.
Researchers then constructed an artificial sky over the cage containing the mice, and simulated the changes in brightness and colour that occur naturally throughout the day/night cycle. It was then observed that their body temperature would peak just after sunset, when the light was a dark blue color.
By comparison, when only the brightness was changed, the mice were most active before twilight.
From these results, it's theorized that coloured light could be used to alter the internal body clock of humans, which could benefit people who work night shifts or travel to distant time zones.