ΔE 9.0, close: similar, with a visible difference side by side. Administratum Grey is a little lighter than Ravenskill.
Can I use Administratum Grey instead of Ravenskill?
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Administratum Grey is a little lighter than Ravenskill.
Can I use Ravenskill instead of Administratum Grey?
The same difference applies the other way round: Ravenskill 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.