I built mine and painted it Panzer gray. You could also do a simple Africa yellow if you wanted. You'll also want to get some flat black for the tires, and maybe some flat white so you can mix it with your base color to begin creating a faded, weathered appearance--but that's me.
It's a great kit; straightforward and easy to build without a lot of parts. Just be careful when sanding the barrel seams. As I remember, the barrel has a significant taper as it comes off the cradle. It's kinda easy to disfigure the taper.
Looking forward to receiving and building the new PAK40 from AFV club. If it's anything like their PAK 43/41 (I'm building that now), it should be terrific......but I digress.
Good luck!
Gip Winecoff