She’s a lady in red.

Kate Middleton looked radiant in an electric blue coat dress for Easter Sunday services at Windsor Castle yesterday, but one small detail of her look had royal fans going wild.

The Princess of Wales, 41, made a surprising move by wearing bright red nail polish on her fingers for the first time in public since she married Prince William in 2011.

While there are no official rules per se about how women in the royal family can do their nails, it’s been said it was a preference of the late Queen Elizabeth II — who was a devotee of Essie’s pale pink Ballet Slippers polish ($10) — for royal ladies to sport light, natural colors.

However, other royal women such as Princess Eugenie and the Duchess of Edinburgh have worn colored nail varnish in the past.

While Middleton has donned red toe polish on several occasions, she’s never worn dark colors on her hands, choosing to go with a clear or nude manicure, or in many cases, no polish at all.

Most fans seemed to love the change.

“My good sis Kate said: ISSA RED NAIL POLISH KINDA DAY and away she went! Lovely,” one fan commented on the Royal Fashion Police Instagram account.

Another royal watcher added, “The QEII era is over! Red nails! Maybe now we’ll see Kate raise her hemlines.”

Some people pointed out the hypocrisy in the situation after Meghan Markle was slammed for wearing dark nail polish at the 2018 British Fashion Awards.

“Meghan was slaughtered for ‘breaking protocol’ just for wearing a nail polish that wasn’t pink,” one Twitter user wrote. “Now here is Kate Middleton wearing red nail polish, will [sic] we be told of how bold and daring this is?”

It’s unclear what exactly inspired the princess to go bold, but we’ll see if the trend continues as the weather heats up.