The colour cyan in phone screens could be the reason you are not getting to sleep

The colour cyan (bluey green) could be a key reason why phone screens stop people falling asleep – and future screens could be redesigned to help us drop off, researchers have said.

Researchers from the University of Manchester say that cyan affects melanopsin cells in the eye which detect light, normally in the daytime.

The researchers created a screen where they could adjust cyan levels – and found that the 11 volunteers felt more alert when it was turned up, and more sleepy when it was turned down.

The volunteers were shown a film with cyan levels turned down, and their saliva tested highly for sleep chemical melatonin after watching it.

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Professor Rob Lucas said: ‘This outcome is exciting because it that tells us that regulating exposure to cyan light alone, without changing colour, can influence how sleepy we feel.

‘Our study also shows how we can use that knowledge to provide a next generation of visual displays.

‘We built our melanopic display by adapting a data projector, but we would expect that this design could be applied to any type of display.’

He added: ‘Such displays could, for example, help phone obsessed teenagers to fall asleep, or support alertness in people who need to use a computer at night.

Dr Annette Allen continued: ‘The new display design could actually have a wider benefit, as it seems that this technology also improves image appearance.

‘Like adding salt to food, we aren’t necessarily aware that it’s been done though we appreciate the effect.’