ΔE 6.9, close: similar, with a visible difference side by side. IJA Gray is a little lighter, cooler than Dark Imperial Khaki.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). IJA Gray is a little lighter, cooler than Dark Imperial Khaki.
The same difference applies the other way round: Dark Imperial Khaki is a little darker, 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 Dark Imperial Khaki on the colour wheel See IJA Gray on the colour wheel
All matches: Dark Imperial Khaki equivalents · IJA Gray equivalents