Mid Imperial Khaki vs Donkey Grey

How close are they?

ΔE 19.2, loose: different enough that you should pick on purpose. Donkey Grey is a little lighter, much more muted than Mid Imperial Khaki.

Can I use Donkey Grey instead of Mid Imperial Khaki?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Donkey Grey is a little lighter, much more muted than Mid Imperial Khaki.

Can I use Mid Imperial Khaki instead of Donkey Grey?

The same difference applies the other way round: Mid Imperial Khaki is a little darker, much 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.