ΔE 15.3, loose: different enough that you should pick on purpose. Thar Brown is more muted, warmer than Light Imperial Khaki.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Thar Brown is more muted, warmer than Light Imperial Khaki.
The same difference applies the other way round: Light Imperial Khaki is more saturated, 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 Imperial Khaki on the colour wheel See Thar Brown on the colour wheel
All matches: Light Imperial Khaki equivalents · Thar Brown equivalents