ΔE 12.3, fair: the same colour family, but not a straight swap. IJA Light Grey Green is more muted, cooler than Undead Flesh.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). IJA Light Grey Green is more muted, cooler than Undead Flesh.
The same difference applies the other way round: Undead Flesh is more saturated, 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 Undead Flesh on the colour wheel See IJA Light Grey Green on the colour wheel
All matches: Undead Flesh equivalents · IJA Light Grey Green equivalents