Why Kate Middleton never wears red nail polish

Catherine wears her own custom blend nail polish. Photo / Getty Images

It may be her sartorial choices that command attention at public engagements but eagle-eyed royal fans have noticed something rather unusual about the Duchess of Cambridge's style.

Indeed, Kate's fans noted that she never wears coloured nail varnish and instead always opts for natural or nude shades.

There's a very specific reason behind her seemingly subconscious choice - and it's all down to the Queen, reported the Daily Mail.

According to Marie Claire, only natural-looking nails are permitted at official royal events.

If Kate isn't wearing the Queen's trusty Essie Ballet Slippers shade on her talons, she likes to mix two polishes together.

Kate learned the manicure trick from Camilla's manicurist, Marina Sandoval from the Jo Hansford hair salon in Mayfair. The Duchess of Cornwall arranged for Sandoval to drive to Clarence House to give both women's hands the once-over ahead of the royal wedding in 2011.

She treated Kate to a £36 ($52) "signature manicure", which includes a luxury soak and exfoliation of the hands, a deep tissue massage to stimulate growth, followed by filing, buffing and polishing.

Sandoval revealed that she blended a special mixture of colours to apply to Kate's nails, including Bourjois no 28 Rose Lounge, and Essie 423 Allure.

"Catherine wanted something very natural looking and I felt these matched her skin colour beautifully. She wanted something off-white and bridal, so these were absolutely perfect," she explained.

"She was very pleased with the result and told me that it looked beautiful and elegant."

The Queen has certainly set a precedent by choosing to exclusively wear Essie's Ballet Slippers since 1989.

According to the polish brand's website, Queen Elizabeth's hairdresser sent Essie a letter in 1989 requesting a bottle of the polish, stating that it is "the only colour Her Majesty would wear".

Essie describes the Queen's choice as a "classic pale pink polish", that is "graced with a subtle, sheer finish".

The brand told ES magazine that Kate and the Queen have bought the polish, saying: "We're incredibly proud that the Queen and Kate Middleton have enjoyed our products over the years."