Hi Konstantin,
Example for variability in standard 1943 NKAP camouflage scheme:
yes, they suggested two patterns to avoid repetitivity.
Anyway, about Il-2s, there was some variation both from plane to plane, both from factory to factory, in facts it's often possible to distinguish the factory that produced an Il-2 by observing some characteristics of the camouflage.
For example, Il-2s produced in Z.1 according to the variant n.1 had very sharp and contrasted camo on the rear fuselage and wings. Those of Z.30 had a more blurried camo with simplified forms, and the bands on the wings were more or less parallel to the flight axis. Those of Z.30 had a more variable camo, often recognizable for a brown rudder.
Some planes have still an uncertain identification, could be planes of Z.30 or planes of Z.1 with the variant n.2 of the pattern, more blurried as the planes of Z.30. Lots of photos at
http://mig3.sovietwarplanes.com/il-2/il-2.htmI've not made deep researches on Yaks till now, so at present time I don't know if the factory that built them is recognizable from the pattern.
Regards
Massimo