What dress does Keira knightly wear during the party in atonement?

Keira Knightley's dress during the iconic party scene in Atonement is a pale green silk dress, which is often described as mint green.

It's a simple, elegant design with a fitted bodice and a full skirt, which falls to her ankles. The dress has thin straps and a low, scooped neckline.

It's notable for its subtle beauty and contrasting color against the dark, smoky atmosphere of the party.