More than 495,000 new grey cars were chosen in 2018, according to the Society of Motor Manufacturers and Traders (SMMT).
With 21% of the market share, grey claimed the top spot for the first time since records began in 1996.
Black came in second with 20%, followed by white at 18%, blue with 16% and red at 10%.
Once the nation's long-standing favourite, silver fell out of the top five, with its lowest popularity rating since the late 1990s.
British motorists shunned primary colours, with red, blue or yellow last making it into the top three nine years ago.
Broken down regionally, the trends were slightly different in Scotland, where white was the biggest seller.
However in Northern Ireland and Wales grey remained popular.
New car sales declined overall by 7% in 2018, with the industry blaming a number of issues.
It was not all the usual colours winning though, with orange and beige cars bucking the trend, with an increase of 37% and 28% to claim seventh and 10th place respectively.
Beige made its first top 10 appearances since 2014, as a number of new and upgraded models had the colour as an option.
Yellow and cream plunged by 34% while orange soared by 37%.
Cream and yellow cars were the biggest losers, both falling by 34%.
Mike Hawes, the SMMT's chief executive, said: "There are more opportunities than ever to personalize your new car to your exact taste, and UK motorists have approached the challenge with gusto in 2018.
"With around 80 new or upgraded models coming to market in 2019 equipped with the latest low and zero-emission powertrains, advanced safety tech and exciting comfort and convenience features, it's great that buyers have so much to choose from."
