ΔE 18.8, loose: different enough that you should pick on purpose. Dusken Green is noticeably lighter, more saturated than Forrest Flux.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Dusken Green is noticeably lighter, more saturated than Forrest Flux.
The same difference applies the other way round: Forrest Flux is noticeably darker, 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 Forrest Flux on the colour wheel See Dusken Green on the colour wheel
All matches: Forrest Flux equivalents · Dusken Green equivalents