Hello Adrian,
You have a lot of options with this figure. You can do him as infantry with the blue facings, artillery with red facings or cavalry with yellow facings. The cavalry yellow tended to be a medium share; not a deep yellow. If you go with buff facings you would have a staff officer. The picture Malc posted is pretty close to the imported British "Army Cloth" but I think the blue on the facings is closer to the British Royal Blue usually found only on a few imported jackets.
These original trousers were made using imported French Light Blue cloth which is also IMHO a better choice for infantry facings. The original jacket which you can just make out is most likely imported British Army cloth and is quite dark.
Keep in mind that Black was quite frequently used for infantry facings and even specified by some states is the proper color. That gives you another accurate color scheme.
Trousers can be grey, French Light Blue or even dark blue and you would still be historically on safe ground.
You have a wide range of greys to chose from. The first picture below (a reproduction jacket) is a typical jean cloth mix of a medium shade but can range lighter or darker
The second picture is an original a jean brownish grey uniform. Again IMHO a very common color produced by local fabric mills and used both for government depot issued uniforms as well as private tailored uniforms.
Since this is an officer, I would avoid the tan "butternut" color.
With the overcoat you have a lot of freedom because locally made, privately purchased overcoats, depot issue, or re-dyed capture Federal overcoats. You can even go with black and a red lining.
