George,
you can definitely paint it Panzer Grey, or with a nice whitewash:
the first /9 Ausf. C was produced in June '42, entered service in July '42 and the last one in May '43.
(Then production swithced to the Ausf D)
So I guess about half were originally delivered in PzGrey.
(The new Nuts&Bolts is what you need for inspiration

)
HTH
Rob