ΔE 10.5, fair: the same colour family, but not a straight swap. IJA Grey Green is warmer than Gray FS26440.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). IJA Grey Green is warmer than Gray FS26440.
The same difference applies the other way round: Gray FS26440 is 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 Gray FS26440 on the colour wheel See IJA Grey Green on the colour wheel
All matches: Gray FS26440 equivalents · IJA Grey Green equivalents