Jeff, if it's any consolation, the kit was the main feature in Military Modelling magazine this month, but no references were included to that colour scheme or to any materials that might point to it. I only managed to find the same photos that I guess you did and agree that it is a pale looking colour, nothing like the German army dark grey.
Unless you can find colour references to Austrian police uniforms of that period, which might offer a clue as to where they were at in terms of looking like soldiers or deliberately distinguishing themselves from the army , then you're in the realm of speculation. Grey seems likely, but then green or even blue don't seem impossible.
There's always Frenchy of course, he often pulls something out of nowhere... If nothing else comes from this post at least it's been bumped again.
