ΔE 11.2, fair: the same colour family, but not a straight swap. IJA Grey Green is a little darker, more saturated, warmer than Light Gray.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). IJA Grey Green is a little darker, more saturated, warmer than Light Gray.
The same difference applies the other way round: Light Gray is a little lighter, 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 Light Gray on the colour wheel See IJA Grey Green on the colour wheel
All matches: Light Gray equivalents · IJA Grey Green equivalents