ΔE 14.6, fair: the same colour family, but not a straight swap. Nurgling Green is a little lighter, more saturated, cooler than Green FS 34258.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Nurgling Green is a little lighter, more saturated, cooler than Green FS 34258.
The same difference applies the other way round: Green FS 34258 is a little darker, more muted, 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 Nurgling Green on the colour wheel
All matches: Green FS 34258 equivalents · Nurgling Green equivalents