The Prussian army in the later Napoleonic period wore a variety of uniforms. The reserve regiments were to wear the standard Prussian Reserve uniform a simple grey tunic cut in a style similar to the Line regiments but without any "tails". However due to the influx of men and little materials some regiments wore uniforms purchased from the British or some even still wore the uniforms they wore when fighting for the French. All uniforms were modified by the wearer to look more "Prussian" such was the strength of the national pride unheard of pre-Napoleon.
The two main styles of uniform were the Kollet and the Litewka. The Kollet is often associated with the Line infantry. Its a solid tunic made from a dark blue cloth for everything except for Jaegers who wore green. Turnbacks were always in red. The collars and cuffs colours denoted what region the unit was from. The straps were white except for the Fusiliers who wore black cross straps.
Here are some examples from my 28mm Army for Lasalle:
Mounted Jaeger Officer his red collar denotes he is from a West Prussian Regiment. He is wearing the Kollet.
Note the black straps for the cartridge box for light infantry and the red turnbacks.
2nd Regiment of Dragoons, 1st West Prussian. This unit is a West Prussian unit but didn't have the traditional red collars. They wore a light blue Litewka with white facings.
The horse has a uniform as well, light blue and lined with white just like the rider.
Standard Kollet for this line regiment, Red collars and cuffs.
Note the white straps and the coat tided across the chest. This is a universally Prussian thing and common in both line, reserve and landwehr.
Landwehr wear the Litewka, note the West Prussian red in the collars.
White shoulder straps denotes 1st squadron. The horse also has red facings. White and black pennons denotes landwehr.
Landwehr infantry did not wear the covered Shako instead they wore cap lined with the regiments facing colour. This is the first battalion of the Westfalen regiement. The wear the Litewka.
This is a foot artillery officer. While it looks similar in style to the Litewka it is made from a much nicer cloth to the uniforms issued to the Landwehr.
While I don't have any Uhlans in my collection they wore the Kollet even though they were issued with the warmer Litewka. It is believed that they refused to wear the Litewka because it would make the look identical to the Landwehr cav. Something that those proud lancers would need want to be mistaken with.