This is apparently the one royal rule Princess Diana always broke

You may have noticed this one...

Doesn't it feel like every day there's a new, random royal rule? The royal women can't wear trousers around the queen, they can't go to bed before the queen and they can't take selfies. And that's just the tip of the iceberg. One woman who chose to ignore royal rules was Princess Diana. The princess famously ignored one rule in particular - the rule of only wearing nude nail polish. Princess Diana used to rock bright red nail polish at high profile events, and why not? A royal no-no. The Queen only approves of one nail colour - Ballet Slippers by Essie. This is the nail colour that the lovely Meghan Markle wore on her wedding day! However, red nail polish wasn't the only way the late Princess Diana added colour to her beauty routine. She became somewhat famous for her use of blue eyeliner, which sparked a pretty iconic makeup trend. A beauty icon.