The event, held at Glencairn House, had 300 people in attendance, including soccer player Brian O'Driscoll and writer Sinead Burke.
This is only the second time Markle has worn colour since her May 19 wedding to Prince Harry, the first being at a reception last Thursday, for which she chose a yellow Brandon Maxwell dress.More news: Weinstein Pleads Not Guilty To New Charges, Released On Bail
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However, there was one aspect of their outfits which were nearly identical - their shoes.
Kate Middleton and Meghan Markle joined the princes for a service at Westminster Abbey.
The Duchess of Sussex looked stunning in a demure, belted black dress from Dior with her favored boatneck neckline and a wild, Stephen Jones fascinator that she makes look chic.
This includes attending a Gaelic sports festival at Croke Park and a summer garden party at the British Ambassador's residence. Before heading back to London, they'll also visit DogPatch Labs, a co-working space for tech start-ups.
Kensington Palace said the couple were "looking forward to learning more about Ireland's history and experiencing its rich culture, as well as meeting the people who are shaping the country's future".