I understand (rightly or wrongly) that the two Battalions of the Frei Corps von Kleist Infantry (Pandour / Green Croats) had flags. I also believe that no record of what they looked like can be found. My question to the forum is; what do you think would make a suitable flag? Maybe Frederick's initials in silver on a dark green background? For your consideration.
Have you checked Kronoskaf Seven Years War Project for detail? link They don't have any details on the Croat standards but given the detail on the other units of this Korps, your idea would seem a good one. Cheers, Rohan.