London, April 19 (IANS): Ever wondered how animals know when to call it a day and return to their shelters? The colour of light has a major impact on how the brain clock measures the time of the day and on how our physiology and behaviour adjust accordingly.

"This is the first time that we have been able to test the theory that colour affects our body clock in any mammal," said lead researcher Timothy Brown from the University of Manchester in Britain.

The research can be applied to humans too.

"So, in theory, colour could be used to manipulate our clock which could be useful for shift workers or travellers wanting to minimise jet lag," Brown pointed out.

The researchers looked at the change in light around dawn and dusk to analyse whether colour could be used to determine the time of day.

Besides the well known changes in light intensity that occur as the sun rises and sets, the scientists found that during twilight, light is reliably bluer than during the day.

The researchers next recorded electrical activity from the brain clock while mice were shown different visual stimuli.

They found that many of the neurons were more sensitive to changes in colour between blue and yellow than to changes in brightness.

The study appeared in the journal PLOS Biology.