Recon89
... various paints being mixed and applied in the field there are many variations.
Well yes and no. Dunkelgelb was a factory applied colour made official in Feb. '43. There might have been an official change to it's look when it was given the RAL number 7028, as prior to that the shade being used was the same as that applied to farm machinery.
Main reason various shades can be found is due to the fact there was more than one paint manufacturer, and later in the war, pigments could and would become scarce.
About ten years ago, Tomas Chory published a book Wehrmacht Heer Camouflage Colors 1939 - 1945, and among his colour chips he provides four examples for dark yellow plus Dunkelgelb nach Muster (the farm machinery paint). I'd post a link, but even on the internet you can find a variety from just that one scanned page - so I don't know which of the googled images is the most accurate (in terms of his book).
regards,
Jack