ΔE 24.8, loose: different enough that you should pick on purpose. Army Green is a little darker, much more muted, warmer than Rainforest.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Army Green is a little darker, much more muted, warmer than Rainforest.
The same difference applies the other way round: Rainforest is a little lighter, much more saturated, cooler.
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 Rainforest on the colour wheel See Army Green on the colour wheel
All matches: Rainforest equivalents · Army Green equivalents