ΔE 18.7, loose: different enough that you should pick on purpose. Yellow Green is noticeably darker, cooler than Malignant Green.
✓ Herrick Games paint comparison chart lists these two as equivalents.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Yellow Green is noticeably darker, cooler than Malignant Green.
The same difference applies the other way round: Malignant Green is noticeably lighter, 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 Malignant Green on the colour wheel See Yellow Green on the colour wheel
All matches: Malignant Green equivalents · Yellow Green equivalents