Napflags (hosted by Ian Croxhall's Warflags) has a brief on Russian flags, including the 1803 assignment to Inspections here
. That gives you a place to look for what regiments were assigned to what Inspection.
Phillip J. Haythornwaite's The Napoleonic Source Book
provides the following uniform for the inspectorate period:
Dark green jacket
Collar and cuffs of inspectorate color
Shoulder straps of seniority color within the inspectorate
Black gaiters or knee boots (depending on Summer or Winter)
Black shako with black cockade edged in orange
Pompom in battalion color (white for the 1st battalion, yellow for the 2nd, red for the 3rd) center in regimental color.
Leather work was white
Inspection colors were as follows:
St. Petersburg: Red
Lithuania: Light Green
Dneister: Lilac pre-1805, then dark green with red cuffs
Caucasus: Medium Blue
Crimea: Light ochre
Seniority colors were:
1st: Red shoulder straps
2nd: White shoulder straps
3rd: Yellow shoulder straps
4th: Raspberry shoulder straps
5th: Turquoise shoulder straps
6th: Pink shoulder straps
7th: Light green shoulder straps
8th: Grey shoulder straps
That should get you started. I can dig in my Funcken or Hourtoulle books for specific details if you give me a specific regiment.
The Hourtoulle 1807, From Eylau to Freidland
is also worth a look.