This is mostly for my own reference, but hopefully it will serve to help others who start out clueless. The following paint scheme should work for the Irish War of Independence, the British Expeditionary Force in WW2, and a Very British Civil War.
All colors are Vallejo Model Color.
I’m also using the following for the officers.
Coats – 1:1 Olive Grey:Green Grey
Sam Brown Belts – Beige Brown