ΔE 28.3, loose: different enough that you should pick on purpose. Septic Green is noticeably lighter, much more saturated, warmer than Elysian Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 28). Septic Green is noticeably lighter, much more saturated, warmer than Elysian Green.
The same difference applies the other way round: Elysian 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 Elysian Green on the colour wheel See Septic Green on the colour wheel
All matches: Elysian Green equivalents · Septic Green equivalents