ΔE 7.5, close: similar, with a visible difference side by side. IDF/IAF Green is a little lighter than Fallen Grass.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). IDF/IAF Green is a little lighter than Fallen Grass.
The same difference applies the other way round: Fallen Grass is a little darker.
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 Fallen Grass on the colour wheel See IDF/IAF Green on the colour wheel
All matches: Fallen Grass equivalents · IDF/IAF Green equivalents