A true fashion icon, Kate Middleton appears at each of her media appearances with a very sharp look. Scrutinised by the local and global tabloids, her outfits are always subject to precise decoding. While she often relies on designer articles of clothing, she sometimes falls for pieces from Sandro, Massimo Dutti or Petit Bateau. On the accessories side, she has already displayed herself with earrings which cost less than £10 from the Accessorize brand.If in terms of style, the Duchess of Cambridge is entitled to a few eccentricities, while in terms of beauty, she has to stick to a rather strict protocol. While she always displays impeccable hair and make-up that perfectly underlines her facial features, George, Charlotte and Louis' mother never has her hands manicured with coloured nail polish. Whether it's classic shades like red and burgundy or more original shades, she is not allowed to wear them. The reason? The queen does not think it is elegant. So she almost never wears nail polish.At her wedding, Kate Middleton had allowed herself a subtle manicure: a mix of the shades Allure d'Essie and Bourjois' Rose Lounge, as told by Marina Sandoval (a London nail-artist) to the Daily Mail.But this is not the first time Elizabeth II has influenced the beauty choices of one of the women in her family. During her 15 years under the British crown, Lady Diana was not allowed to change her haircut at the risk of overshadowing her mother-in-law.