ΔE 15.0, loose: different enough that you should pick on purpose. Sap Green Hue is a little darker, more saturated than Army Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Sap Green Hue is a little darker, more saturated than Army Green.
The same difference applies the other way round: Army Green is a little lighter, more muted.
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 Army Green on the colour wheel See Sap Green Hue on the colour wheel
All matches: Army Green equivalents · Sap Green Hue equivalents