ΔE 7.8, close: similar, with a visible difference side by side. Grey Brown is a little darker, more muted than Olive Drab 1.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Grey Brown is a little darker, more muted than Olive Drab 1.
The same difference applies the other way round: Olive Drab 1 is a little lighter, 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.
See Olive Drab 1 on the colour wheel See Grey Brown on the colour wheel
All matches: Olive Drab 1 equivalents · Grey Brown equivalents