Carnation, Lily, Lily, Rose by John Singer Sargent, 1885-6
This is one of my all-time favourite paintings (and painters). It's on permanent display at the Tate Britain. It was painted outdoors in order to capture the light at dusk. The girls are Dolly and Polly Barnard, the daughters of one of Sargent's friends.
(image via tate)