Michael
Most Pak 40's were monotone - gray or yellow. Paint was not an item usually issued to Pak 40 gun crews, only the occasional gift of Whitewash. These guns were quite often towed by trucks, not just halftracks (as the latter were far more expensive than trucks and were required for other duties) and trucks were not issued camo paint.
Due the limited supply of paint granted for use on the other vehicles used to tow them, the gun crews relied on ground cover, bushes, reeds, branches, etc to break up the guns outline. When they did camo, it was from paint 'acquired' elsewhere, and the pattern was whatever they felt like doing and usually limited to only the barrel and gun shield.
But hey, paint it what you want - there were exceptions to every rule.