ΔE 19.9, loose: different enough that you should pick on purpose. Fallen Grass is a little lighter, more muted, cooler than Mid Soviet Khaki.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Fallen Grass is a little lighter, more muted, cooler than Mid Soviet Khaki.
The same difference applies the other way round: Mid Soviet Khaki is a little darker, more saturated, 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 Mid Soviet Khaki on the colour wheel See Fallen Grass on the colour wheel
All matches: Mid Soviet Khaki equivalents · Fallen Grass equivalents