As for the shades. German WW2 paint was produced in 3 factories, and they all produced different shades. As the war went on, those shades changed, so depending on whose paint was used and when it was applied, it would be unlikely to match anything else.
NATO colours are even worse. Although there is a standard NATO camo scheme, each country produces its own paint, so NATO tanks from different countries will be a different colour.
Yours looks excellent, really like it. If you weather it afterwards it will come to life.
