From Wikipedia; image lightened to bring out detail.
Elizabeth wears a black ensemble - hat and feayhers and dress broken up by a white partlet in this Peter Ernst Rockstuhl portrait.
Keywords: 1817, Rockstuhl - Peter, Elizabeth Alexeievna, Princess, Tsaritsa, Baden family, Romanov family, Russian, feathered hat, strap, partlet, scoop neckline, bodice, sweetheart décolletage, long upper puffed sleeves, waist band, Empire waistline