A blue hat with large flowers and white gloves completed her look.
Zara Tindall, 38, also chose a floral dress, pairing it with a baby blue hat worn on top of her head. A pair of drop pearl earrings could be seen in her ears.
The mum-of-two wore her blonde hair in an updo under her hat, and kept her makeup simple.
Not to be outdone, Princess Beatrice also stepped out in blue tones. She chose a lace shirt dress which had three-quarter length sleeves and came down past her knee.
A wide brimmed hat in a matching shade added another splash of blue to her outfit. The dress was belted at the waist to show off her slim frame.
The Royals are usually careful to ensure that they all wear different colours from the Queen – but it seems on this ocassion they decided to all wear the same.
What is the Royal Ascot dress code?
Known for being strictly implemented, the Royal Ascot dress code is one of the tightest in the racing world.
Royal Ascot produce a detailed guideline every year for guests to follow to ensure there are no style blunders.
The most stringent rules apply in the Royal Enclosure, with ladies having to wear dresses or skirts that fall just above the knee or longer.
Straps must be one inch or greater, with strapless, halter neck and spaghetti straps banned. Midriffs are also not allowed to be on display.
While trouser suits are allowed, they must be full length on the leg and matching material and colour.
Most importantly, hats must be worn, although headpieces with a solid four inch base are permitted. Fascinators are not allowed.
Men must wear black or grey morning dress which includes a waistcoat, tie, top hat and black shoes worn with socks.
This dress code is followed not only by guests but also by members of the Royal Family who attend.
The Queen Anne Enclosure and the Village Enclosure are slightly more relaxed, with fascinators allowed, and dresses or tops with thin straps permitted.