Dear Conor,
With Soviet uniforms it is hardly impossible to make mistakes with colors.
For many reasons:
Industrial standards were not like today. Various state owned industries produced the ordered items acc. their ' own' standards. They used the available basic raw materials, thus creating quite a variation in color. E.g. in one of the best books about the Soviet soldier, " The Soviet Soldier of World War Two" by Philippe Rio, Histoire & Collections, ISBN 9778-2-35250-100-8, pag. -51-, a collection of pilotka's (side caps) is shown, which vary from a sort of olive drab, via dark yellow, khaki, sand to Russian green.
Furthermore, due to weather influences (bleaching sun light), washing turns etc., the colors faded out rather quick (even my modern Dutch uniform fades out remarkably after some months of use!).
So, do not bother too much. It is diffecult to go wrong. It even makes it easier to get some variety in your build.
Looking forward to see the results,
P.