ΔE 38.3, loose: different enough that you should pick on purpose. Poison Green is noticeably lighter, much more saturated, warmer than Ferocious Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 38). Poison Green is noticeably lighter, much more saturated, warmer than Ferocious Green.
The same difference applies the other way round: Ferocious Green is noticeably darker, much more muted, 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 Ferocious Green on the colour wheel See Poison Green on the colour wheel
All matches: Ferocious Green equivalents · Poison Green equivalents