ΔE 15.7, loose: different enough that you should pick on purpose. Fern Green is a little lighter, cooler than Gung-Ho Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Fern Green is a little lighter, cooler than Gung-Ho Green.
The same difference applies the other way round: Gung-Ho Green is a little darker, 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 Gung-Ho Green on the colour wheel See Fern Green on the colour wheel
All matches: Gung-Ho Green equivalents · Fern Green equivalents