There were two distinct shades of this color. One, called Dunkelgelb nach Muster (Dark Yellow to the standard) was closer to the yellower, more mustard color. It was apparently used as an agricultural color for painting farm equipment, like John Deere green. It was not satisfactory, and the official shade, RAL 7028, was adopted.
Here's where it gets tricky, and Tom Jentz would not agree with me: while the STANDARD for Dark Yellow did not change during the war, the actual colors were not all the same. First, paints were produced by many manufacturers in different parts of Germany. Plants producing military vehicles in northern Germany used paints from different paint makers than plants in Bavaria, or East Prussia, or elsewhere. Second, as the war progressed, more and more raw materials for paint became unavailable and had to be replaced. This often altered the shade of the color, and the same thing happened in the US when Cadmium Green was disallowed for paint because cadmium was needed for treating metal alloys for war production. Finally, difficulties in obtaining even approved paint ingredients required substitutions.
Also, supplies of older colors or obsolete shades were often used to make other related colors. Left over tropical colors from the failed African campaign were used to make Dark Yellow, and there were formulas to show how to mix the newer colors using the old paints and mixing tints supplied by the paint makers. Some of the desert shades were not that far off from RAL 7028 Dark Yellow, and may have been used in a pinch without remixing. With secondary colors being applied over the base color, it would be almost impossible to tell. I have several pieces of German field gear I bought when I was re-enacting, and no two match each other, and none of them match the standard chips in my copy of Tomas Chory's excellent book on German camouflage. You can't go too far afield without getting into trouble, but there were likely as many variations of Dark Yellow as there were for Olive Drab.
That said, the standard shade of Dark Yellow was warmer and tanner than the yellow-mustard color first used in small amounts. It is, however, a very complex shade that changes color in different lights, which for a camouflage color is a good trait. For us the modelers, it's a pain in the buttinski.....
A number of modelers who use acrylics use the Tamiya Dark Yellow cut with Desert Tan or Buff to lighten it. It's better to vary the color slightly from model to model, as you should for Olive Drab as well.
