If you use the two kit figures, the standing full figure and seated interior figure along with the radio set, there is practically nothing else that can be seen down through the open turret.
The interior of the hull below the turret was very likely ivory and the interior of the turret was likely the factory exterior camouflage color (Panzer gray for an early vehicle).
A way to disguise the essentially empty interior would be to paint the entire inside flat black. The paint ivory only on the few spots that are clearly visible through the opening(s) feathering that color into the flat black. You want to essentially paint in a shadow increasing to total black from the center of the visible spot to its visible edges. You can also use the same technique on the figures and other larger interior structures, fully painting only the clearly visible areas and then fading the rest from there to total black.
I don’t have any particularly good photos of this process of the interior of a model (I’ll keep looking), but here’s a quick sequence of a single torso figure to illustrate the idea. The visible portions are fully painted, but the rest simply fades to total black inside the black interior. The only interior areas that have any other color are the ones just inside the side hatch coaming.
So, a quick search though my happy-snaps and I found this one showing how the interior color (here a blue gray instead of ivory) has been faded into the flat black that the rest of the engine compartment has been painted in. The little bit of visible color can just be seen through the cooling air grill mesh on the finished model and the black totally disguises the rest of the empty interior in this area.
