The Airfix StuG III represents an Ausf. G model manufactured in early 1944, because it has the late production 'pot' mantlet (eroneously called 'saukopf' mantlet in some text books...) without the coaxial MG, but still has the loader's MG shield rather than the remote control roof MG. The coaxial and remote control MG versions being produced later in 1944. As such it should be painted in overall dark yellow and either left as such or with a crew applied camo pattern in light olive green and/or red-brown. Being crew applied, it could be sprayed, brushed, mopped or wiped as described above. The camo paints came as a paste and could be thinned with paint thinner, petrol, oil or even water, all of which resulted in a lot of color and fading variation. Patterns could be dots, patches, thin strips, wide strips or any combination! From around October 1944, standard patterns were supposed to be applied on new vehicles at the factory, initially using the same three colors. Later, the olive green was applied as the base and the yellow and red-brown applied in patterns over the top. Later still, the red-lead primer was left as the base with yellow, green and sometime red-brown patterns oversprayed. Dunkelgelb came in several shades varying from a kind of dark cream to a sand-yellow and there is much argument all over the internet as to what it looked like! My personal preference is to use Humbrol 94 for the dark yellow, Humbrol 86 for the olive green and Humbrol 160 for the red-brown, if that helps. If you wanted to make a StuG in the earlier dark grey, you would need to modify it back to at least an early Ausf. G with the square mantlet. Though very few Ausf. G were made between December 1942 and the cutover for dunkelgelb in February 1943.