A brief Google reveals that the Danish wore blue grey uniforms with Jack boots and French style grey kepis. So, Austrians? Some commentators say many units were still wearing the midnight blue uniforms (the latter greatcoats persisting until 1940). So you could use Belgians, Chasseur a Pied or even 1864 Danes..
I certainly wouldn’t bother painting up a bunch of Danes specially.
"Mistakes in the initial deployment cannot be rectified" - Helmuth von Moltke