my choice would be flat black or a dark charcoal gray. the original HAT Uhlans were made of that color & it looked fantastic! i know a lot of people will dsiagree with this, but many Prussian units of the time wore black & it will be a nice contrast to the current colors to other army's sets.

I'd go for medium blue or grey.

I came late to the party but count me in as saying whatever color the non-painting crowd prefers is fine by me. Once the primer starts flying they're all the same to these eyes.

Nice of SR to ask, as always.