We are going to talk about classic rule of etiquette of Queen Elizabeth. The rule states that colored manicure or fake nails are not allowed on anyone residing at the Windsor Castle. It is considered vulgar according to British OK. Whenever Kate Middleton prepares for major event such as her sister's Pippa's wedding, she uses the only allowed trick and that is a very see through nail polish Ballet Slippers by Essie. 

Official Essie site features time scale with proud highlight: Queen Elizabeth's helpers buy Ballet Slippers for the last 28 years.  For her own wedding to Prince William, Kate chose Ballet Slipper's neighboring color Allure and asked to add few drops of Rose Lounge from So Laque collection from French brand Bourjois.

Natural color became favorite of many actresses, singers, trendy fashion editors and models. Model Gigi Hadid doesn't use bright colors even for the dinner in honor of her favorite designer and mentor Karl Lagerfeld.