ΔE 7.0, close: similar, with a visible difference side by side. Dirty Grey is a little darker, cooler than Mid Mustard Khaki.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Dirty Grey is a little darker, cooler than Mid Mustard Khaki.
The same difference applies the other way round: Mid Mustard Khaki is a little lighter, 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 Mid Mustard Khaki on the colour wheel See Dirty Grey on the colour wheel
All matches: Mid Mustard Khaki equivalents · Dirty Grey equivalents