ΔE 8.7, close: similar, with a visible difference side by side. RLM 66 Black Gray is a little lighter than Dryad Bark.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). RLM 66 Black Gray is a little lighter than Dryad Bark.
The same difference applies the other way round: Dryad Bark is a little darker.
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 Dryad Bark on the colour wheel See RLM 66 Black Gray on the colour wheel
All matches: Dryad Bark equivalents · RLM 66 Black Gray equivalents