Due to the very interesting discussion I rediscovered the Tableau by Petzinger about the Prussian Army, in partial to be seen on the dust jacket by the book of Merta – and fully in Bleckwenn's Unter den Preußen Adler.
Though it is guessed to be of 1770 origin, it looks quite close to 7YW to me – showing all the free corps for example.
Two problems, the illustrations I do have are quite small and next the mirroring effect of light, when doing photos, and really third problem, Prussian Army of 7YW is only a side kick interest and I am more or less an interested amateur (main interest French Revolutionary Wars 1792 – 1800)
I present some photos of the tableau, to just give examples what is there.
One interesting point to observe, the different shades of Prussian dragoon coats, while later (Menzel, Thieme) show clearly an overall darker hue, sorry for the quality.
As with such tableaus, which were highly fashionable, it is difficult to asses from where the artist drew his source or conclusion, but Petzinger looks pretty much convincing also in detail and he did other very interesting studies about the army of Hessen Darmstadt, where I also enclose a photo of regiment Erbprinz of about 1750 (which shows all classic 7YW style in my view, very short and tight sleeves, thin lapels, short tunics, long waistcoat and openend up waistcoat (I leave this for debate though, as there is at least another primary source which shows them buttoned up a bit higher.