ΔE 28.6, loose: different enough that you should pick on purpose. Sulfur Yellow is a little lighter, much more saturated, warmer than Malignant Green.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Sulfur Yellow is a little lighter, much more saturated, warmer than Malignant Green.
The same difference applies the other way round: Malignant Green is a little 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 Malignant Green on the colour wheel See Sulfur Yellow on the colour wheel
All matches: Malignant Green equivalents · Sulfur Yellow equivalents