Greg, it's a complex theme. But like the late war colors in WWII there are more myths around than facts. Of course the supply situation was critical, of course this was the main reason for the introduction of lozenge tarnstoff. But on the other side, pigments never where on sihort supply, remember that the Reich even traded with them with the US in July 1916. The main shortage was natural bases like oils, natural resins and towards to the end even thinners based on petroleum products.
Reading some descriptions I sometimes have a sneaking suspicion that bad or careless workmanship with correct thinning, careless cleaning of sooty surfaces etc etc took the same toll as bad quality paints.
Concerning the blue Jasta 15/18 paint: Blues are notouressly mediocre covering paints and still are. Even with todays high quality alkyd resin paints it would not be sure that you can't the see the difference between a dark undersurface and a white undersurface. Even today I would suggest to prime a even grey or white coat on a tarnstoff fuselage with crosses already applied.
H