The Grand Duchy of Berg was a German state centered around Dusseldorf that served as a client state of Napoleonic France. Ruler Joachim Murat was (seriously) enamored with the color pink and stylishness, and it showed in the unique uniforms of the Berg Lancers. The original c. 1807 uniforms were the most extravagant, and they are the ones recreated here.
Prompt is "BergLancer", along with "uniform,jacket,pants,shako cap,boots". "White Vest" and "pink jacket" may be useful if you want the most commonly depicted version.