ΔE 9.9, close: similar, with a visible difference side by side. Olive Grey is a little lighter, more saturated than Bone Black.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Olive Grey is a little lighter, more saturated than Bone Black.
The same difference applies the other way round: Bone Black is a little darker, more muted.
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 Bone Black on the colour wheel See Olive Grey on the colour wheel
All matches: Bone Black equivalents · Olive Grey equivalents