According to the seller, the one below is an original German WW1 (1914) tent square (Zeltbahn):

This one is dated 1916 :

AFAIK, Zeltbahns were manufactured in two different colors – ochre and feldgrau. At the start of WW1, Zeltbahns were of an ochre color. As the war progressed, the color was changed to a less conspicuous feldgrau color.
Feldgrau Zeltbahn :

I guess this should be applicable to larger models as well...
H.P.