Yes, along with fake nails, the Duchess of Cambridge has been banned from wearing coloured nail polish.
According to 'insider sources', it's deemed 'vulgar' by the royal family. It's a rule the Queen sticks to herself too (Ever seen her rocking a crimson nail? You haven't, have you?) and one that Meghan Markle also has been abiding by in recent public appearances.
On the bright side, it might make the painful decision of choosing your nail colour at the salon slightly easier?