Don't beat yourself up about this too much.
Whilst the colours produced by the various German paint manufacturers were quite consistent for most of the war (hardly surprising since they were all working to formulae developed by one company, Warnecke and Bohm) things went a bit pear shaped towards the end.
In any case paint varies according to how it is initially applied,then it weathers depending on the environment and finally,for model makers,there is the effect that scale has on our perception of various colours.
many hobby paint manufacturers make paints well matched to original German chips. Xtracrylix (acrylics) and White Ensign Colourcoats (enamel) are my favourites,but I use them as a starting point.
I honestly believe it is pointless trying to exactly match 1940s paints on small plastic models. Try to find something in the right area that looks right on the model. It is art not science,trying to give the impression of how the full scale subject might have looked.
If you present a model with nice blue underside along the lines of any of the popular hobby equivalents and someone says that it doesn't look like RLM 65 then they are talking out of a place where the sun doesn't shine
Cheers
Steve