CELEBRITIES including Rihanna and Cara Delevingne are dyeing their locks grey, #GrannyHair has more than 250,000 posts on Instagram, and 63-year-old grey-haired model Lyn Slater earlier this year followed in the footsteps of Cindy Crawford, Claudia Schiffer and Naomi Campbell to sign with the prestigious Elite model agency.

Grey isn't just taking the fashion world by storm; it's also the colour to be seen in when it comes to new cars.

Ford has just revealed that grey is the most popular choice for its buyers in Europe, knocking white from the number one spot last year.

Britain's top-selling car maker currently offers eight different shades of grey for customers in Europe, and has offered more than 50 shades of grey around the world since the early 1990s.

"We identified grey as a ‘trend colour'- one that has a shorter lifespan than core paints developed around silver, black and white - but even we're surprised at how popular it's become," said Julie Francis, Ford's colour and material design manager.

"Grey is a great untapped colour, offering new ways to be cool and different in the modern age and that makes it exciting and something people are prepared to pay extra for."

It's not only a desire to stand out from the crowd that's driving the trend - recent political upheaval across the globe is also turning us onto grey, according to colour psychology expert Karen Haller.

"When there is a level of insecurity and uncertainty - as we have seen following the US elections and Brexit - we tend to retreat and gravitate towards things that make us safe, which is why grey is so popular," said Haller.

"This trend has really taken off because it is also a colour that recedes, allowing for more vibrant colours to take centre stage. It really depends on your outlook. For me, there's already enough grey in the world - so I love to surround myself with the joy of colour."

But grey represents more than just style and comfort. The colour also has more cerebral connotations, says Laurie Pressman, vice-president of the Pantone Colour Institute.

"Thoughtful and contemplative, grey is the colour of intellect. We refer to the grey matter of brain and mind and thereby associate grey with representing a striving for truth, knowledge and wisdom," he said.