ΔE 6.5, close: similar, with a visible difference side by side. US Field Drab is a little lighter, cooler than Graveyard Earth.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). US Field Drab is a little lighter, cooler than Graveyard Earth.
The same difference applies the other way round: Graveyard Earth is a little darker, 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 Graveyard Earth on the colour wheel See US Field Drab on the colour wheel
All matches: Graveyard Earth equivalents · US Field Drab equivalents