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[i]"An Illustrated Encylclopedia Of Uniforms Of The Napoleonic Wars" has these details for Prussian Dragoon regiments prior to the reforms of 1806.
Light Blue short tailed infantry style coat with the following distinctions.
5.Anspach______Dark Red___White______Dark Red
The 1st, 2nd, 7th, 13th, &14th Regts. had yellow buttons, all the rest had white buttons.
The 8th & 9th Regts. had white laces to the buttons on their chests.
For 1806 the turnback colour might refer to an edging around the turnback which was the same Light Blue as the coat, the text is not entirely clear.
These details are for 1786 onwards, some of the regiment titles appear to have changed over time but there are no uniform changes listed until the reforms of 1806, after which there are only 6 Dragoon Regiments listed who wear the long skirted Kollet coat with the regimental distinctions shown in Carlo Antomio's 'Mont Saint Jean' link.
The first picture at top left of Carlo Antonio's first link shows the short tailed Dragoon coat (rather than the Kollet), but the ilustrations I have show it in a lighter shade of blue .