The fourth of the five new Austrian regiments is I.R. #21.
From 1808-1810: Infantry Regiment ‘Prinz Rohan’ Nr. 21 (Inhaber: Feldmarschalleutnant Viktor-Ludwig, Prinz Rohan von Guem). Earlier, from 1778 - 1808, Gemmingen, and later from 1810 - 1815 Albrecht, Graf Gyulai.
The regiment was recruited in Bohemia, in the Koniggratz area.
In 1809, the regiment fought at Ratisbon, Aspern, and Wagram.
The "meergrun" (sea green) facings are depicted as a turquoise shade by some, so I went with that for this unit, which has brass buttons.