that you have to make a distinction between the standard of the hue and the final paint-product in practice. The standard, RAL colour cards of RAL 6003 and 8017, did not change from 1940 to 1945. Only RAL 7028 changed into RAL 7028 Ausgabe 1944, an isolated act! Paints may always show a little variation but f.e. not in a range from a dark green to a light green, because all of them had to pass through the acceptance process, which based on technical terms of delivery (TL). The TL contained the specific RAL-codes as standard for the hue. If the hue of the paint was too far away of the standard, it would not have passed the acceptance process.
Flaschengrün? Well, the camouflage colors of the former Reichswehr were used and produced until summer 1937. Flaschengrün, one of them, was RAL 6007 (28). So this would mean, that paints produced in 1937, were in stock almost 6 years, before they were used again in 1943. Still in 1938 the maximum storage time of synthetic enamel paints were 3 months and not before 1939 it was a maximum of 12 months! The same with the Reichswehr brown RAL 8010 (18). Resedagrün, which means RAL 6011, was never mentioned in a TL.
In pratictice there are a lot of reasons, why there were darker or lighter colors (mixtures, other colors than the TL-paints, tests, different dilutions, thin layers, weathering etc.).