Most British troops wore khaki in this conflict although they sometimes retained the home service trousers. Puttees seem to have been a variety of colours, khaki, brown, black, blue, depending on lots of things - branch of service, regiment, rank, etc. There are several other threads on here about it.
I painted my Brits' puttees all khaki as it makes the troops useable for other NWF conflict in later years too.