Hello
He is wearing the field uniform for the premier Prussian infantry regiment, 1. Garde-Regt. zu Fuss. The red piping you have painted down the front is also used on the collar edge and on the top and bottom of the cuffs. The collar tab (under the litzen bars) underlay is white, while the actual litzen bars on the collar and cuff are a muted metallic gray. Buttons are in muted silver. The piping on the shoulder boards are actually double piped; white on the bottom and silver piping above. The general's Russian braid on the shoulder boards is a mixture of silver and gold cording with black flecks in the silver portions. Also, the buckle on his feldbinde (belt) is in silver. The strap on the officer's troddel (sword knot) would be black leather with three thin silver stripes along the strap. The knot would stay silver, with the very bottom being black (for Prussia). Hope this is of any help to you.
Regards
Dave