ΔE 22.1, loose: different enough that you should pick on purpose. Bright Green is noticeably lighter, more saturated, cooler than Poison Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Bright Green is noticeably lighter, more saturated, cooler than Poison Green.
The same difference applies the other way round: Poison Green is noticeably darker, more muted, 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 Poison Green on the colour wheel See Bright Green on the colour wheel
All matches: Poison Green equivalents · Bright Green equivalents