The blue and white polka dot belted dress by Alessandra Rich, previously worn by Kate to a Jubilee Big Lunch event just last month was likely a nod to the sustainable theme at the prestigious tennis tournament.
This year, Ralph Lauren redesigned the uniforms for chair umpires, line umpires and ball boys and girls in partnership with The All England Lawn Tennis Club to embrace more sustainable and innovative fabrics using recycled materials.
Evian, the official water sponsor of Wimbledon for the last 14 years, is also encouraging an eco-conscious dress code in their VIP suite, which has been certified as carbon neutral by the Carbon Trust this year.
Kate accessorized her outfit with a few more recycled items from her royal closet, including her Finlay Henrietta sunglasses, recently worn on tour in the Bahamas, and her Mulberry Amberley bag in white, which she has used numerous times before.
Simon Stacpoole/Offside/Offside via Getty Kate Middleton and Prince William
And the finishing touch was a green and purple bow tie pin, signifying her status as patron of the All England Lawn Tennis Club. The club's official colors are dark green and purple, and only a few select people — including the club's president, the committee of management, vice presidents and four members of executive staff — are permitted to wear the bow.
Karwai Tang/WireImage Kate Middleton and Prince William
The Duchess of Cambridge is known for her habit of recycling previously worn clothing — sometimes even years apart! — and she also turns to vintage items. During her Caribbean tour in March, Kate sported a 1950s dress from U.K. boutique Willow Hilson Vintage.
"It was so apt, because it's got all the great Caribbean colors, it's such a reggaeton kind of dress in its color palette — she looks like she is having a whale of a time!" Willow Hilson, the founder of the Cheltenham-based independent boutique, previously told PEOPLE.
Neil Mockford/GC Images Kate Middleton
Kate and Prince William, both 40, sat in the royal box at Centre Court at the annual sporting event to watch Serbian tennis star Novak Djokovic play Italian Jannik Sinner at the men's quarter-finals.
Kate's parents, Carole and Michael Middleton, were also in attendance on Tuesday. They were seated to the royal couple's left in the Royal Box. The Duchess of Cambridge was spotted blowing them a kiss as she and William took their seats.
The royal is a longtime regular at Wimbledon and attended the tennis tournament alongside her family before marrying Prince William.