ΔE 6.8, close: similar, with a visible difference side by side. Pastel Green is a little lighter, cooler than Green FS 34258.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Pastel Green is a little lighter, cooler than Green FS 34258.
The same difference applies the other way round: Green FS 34258 is a little darker, warmer.
ΔE is the colour difference between our two swatch estimates: under about 6 is close, over about 15 is loose. Real paints also differ in finish, coverage and how they thin, so test before you commit.
See Green FS 34258 on the colour wheel See Pastel Green on the colour wheel
All matches: Green FS 34258 equivalents · Pastel Green equivalents