ΔE 9.9, close: similar, with a visible difference side by side. USAF Tan is more muted, warmer than Washable Dust.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). USAF Tan is more muted, warmer than Washable Dust.
The same difference applies the other way round: Washable Dust 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 Washable Dust on the colour wheel See USAF Tan on the colour wheel
All matches: Washable Dust equivalents · USAF Tan equivalents