Kate Middleton learned a lot from her grandmother-in-law, Queen Elizabeth II.

The Duchess of Cambridge not only received secret "princess lessons" from the monarch, like Mia Thermopolis, but also used her knack for wearing one bright color to stand out in a crowd.

On March 14, Commonwealth Day, an annual celebration of the Commonwealth, the Duchess chose a royal blue outfit by one of her favorite designers, Catherine Walker.

She wore a very elegant tailored blue coat over a knee-length dress of the same color and pointed toe heels. She accessorized with a blue hat reminiscent of Britney Spears in Toxic, but the Duchess' was made of rich velvet and had the most beautiful bow at the back, further enhancing her artfully wavy hair.

Prince William, walking by his wife's side, wore a suit and tie in shades of blue.

The Duchess matched her jewelry with her outfit, wearing a sapphire and diamond necklace and earrings, but the colors weren't the only reason she chose the jewelry; according to People, Middleton will wear it when she meets with Ukraine's President Volodymyr Zelensky in 2020. She wore the jewelry when she met with him. By wearing it again, she is sending a subtle but clear message of support for Ukraine and its people as the war with Russia rages.

Outside Westminster Abbey, the Duchess was photographed receiving flowers from her children. Posting one of the pictures on Instagram, the Cambridges wrote, "Wonderful to gather at Westminster Abbey today to celebrate #CommonwealthDay and the modern, vibrant, diverse communities around the world."