What he said!
Frank is right. 1942 Russia was a wild mix of colors on the Steppe. Generally speaking, anything that survived 1941 & made it into 1942, stayed in Grey throughout the year. But new production was coming in different colors, & it's a complicated situation.
On one hand, vehicles were getting painted for DAK & ended up going east at the last minute. Also, new factory production (particularly StuGIIIFs) was appearing in a yellow, although probably not Dunkelgelb. Color researcher Jean Restayn has speculated that the color was a kind of ochre.
In a parade in Paris in June 1942, the LAH's new StugIIIF's were all coated in a solid yellow color; there is film available for this parade. In addition, there is a series of famous color photos of solid yellow StuGIIIFs in the factory district of Stalingrad (with barrels in red primer), 10/42, which is definitely not dunkelgelb.
If you look in Panzer Colors (iirc vol.1), there is a pic of a StugIIIF in Tunisia, same time period as the Stalingrad Stugs, painted exactly the same.
Also, in a Barbarossa edition of Signal, there is the famous aerial photo of a panzer grouping in Russia, in a village, everything in grey, except for one little Kubelwagon that sticks out like a sore thumb...in some kind of ochre. And that is 1941!
Getting back to Blau/42, even solid grey vehicles were getting one of a kind camo patterns with whatever camo colors they had available...usually Luftwaffe RLM colors. The consensus is that one of the Panzer Divs. that went into the Caucausus had it's panzers not in dark Panzer grey, but a solid coating of a lighter RLM grey
Interesting stuff.