ΔE 12.1, fair: the same colour family, but not a straight swap. Japan. Unif. WWII is noticeably darker, more muted than Khaki.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Japan. Unif. WWII is noticeably darker, more muted than Khaki.
The same difference applies the other way round: Khaki is noticeably lighter, more saturated.
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 Khaki on the colour wheel See Japan. Unif. WWII on the colour wheel
All matches: Khaki equivalents · Japan. Unif. WWII equivalents