In men and women of a certain age, the absence of any grey hair can lead to cynical suggestions that they have been reaching for a bottle of dye.
But a study indicates those accusations could be groundless - at least for a lucky few.
Researchers have discovered that one in 10 over-60s does not have any grey hair, which could mean the cloud of suspicion can be lifted from those who - like Selina Scott, 61, the broadcaster, and actresses Cherie Lunghi, 60, Susan Sarandon, 65, and Sigourney Weaver, 62 - seem, against all the odds, to have clung on to the colour of their younger days.
The worldwide study found that the prevalence of grey hair in men and women was less than previously thought. The survey, which is published in the British Journal of Dermatology, was conducted by the research and development arm of the cosmetics manufacturer L'Oreal to establish global trends about when people go grey.
The company may be disappointed by the findings, which indicate the market for its dyes could be smaller than it had hoped.
The researchers set out to test a widely-accepted "rule of thumb" in the cosmetics industry, that by the age of 50, 50 per cent of the population had at least 50 per cent grey hair. In fact, fewer than one in four taking part had that much grey. In many parts of the world, it was a substantially lower proportion.
The research involved an analysis of the natural hair colour of more than 4,000 men and women, from a range of ages and ethnic backgrounds, from more than 20 countries, including Britain.
Overall, of those aged between 45 and 65, 74% had some grey hair, covering an average of 27% of their head.
As expected, the number of people with grey hair increased with age, as did the amount of grey.
Among those aged between 45 and 50, 63% had some grey hair, covering around a fifth of their head. This rose to 78 per cent of people aged between 51 and 55, with an average of 26 per cent of their hair being grey.
In 56 to 60 year-olds, 86% had some grey - an average of almost a third of their hair. In the final category, from 61 to 65 year-olds, 91% had grey hair, over an average of 40 per cent of their head.
Grey hair was more common in men (78%), than women (71%).
In men, it was most likely to start in the temples, spread to the top of the head and then to the back. Among women, it started equally in the temples and at the top of the head.
Earlier this month, Fiona Bruce, 48, the television presenter, admitted that she dyed her hair to stave off any question of her being too old for the screen.