ΔE 29.8, loose: different enough that you should pick on purpose. Moon Yellow is noticeably lighter, much more saturated, warmer than Septic Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 30). Moon Yellow is noticeably lighter, much more saturated, warmer than Septic Green.
The same difference applies the other way round: Septic 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 Septic Green on the colour wheel See Moon Yellow on the colour wheel
All matches: Septic Green equivalents · Moon Yellow equivalents