ΔE 14.1, fair: the same colour family, but not a straight swap. Yellow Green is a little lighter, much more saturated than Malignant Green. They are different kinds of paint: Army Painter Malignant Green is a one-coat contrast-style paint and Vallejo Yellow Green is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
✓ Herrick Games paint comparison chart lists these two as equivalents.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Yellow Green is a little lighter, much more saturated than Malignant Green. They are different kinds of paint.
The same difference applies the other way round: Malignant Green is a little darker, much more muted.
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