
https://www.color-hex.com/color/fdf5b4
Color sampled from 251 storage door above.

https://www.color-hex.com/color/cebd92
Color sampled from SdKfz 9.
Obviously, there is a considerable amount of variation depending on area being sampled, dust, dirt, oil, grease, method of paint application, thinner used, dilution ratio, time of day, lighting conditions, camera, film, processing, monitor settings, Feng Shui, whether the photographer had chocolate milk, etc…
In other words, I doubt this process is going to yield accurate results with so many uncontrolled variables. For what it’s worth, the first one looks a lot like Elfenbein RAL1001.
I just stumbled across this RAL chart, note the 5 shades of Dunkelgelb;
Unless someone has a new, in box, relic of the proper time frame, can confirm that the color of this artifact matches the color of the paint used at Nibelungenwerk during the time in question and also has access to a spectrophotometer to determine its actual color, this method of determining a paint color seems doomed from the start.