ΔE 22.4, loose: different enough that you should pick on purpose. Viridian Green is noticeably darker, more muted than Forest Faun.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Viridian Green is noticeably darker, more muted than Forest Faun.
The same difference applies the other way round: Forest Faun is noticeably lighter, more saturated.
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 Forest Faun on the colour wheel See Viridian Green on the colour wheel
All matches: Forest Faun equivalents · Viridian Green equivalents