ΔE 6.3, close: similar, with a visible difference side by side. Ocean Gray is a little lighter than Necromancer Cloak.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Ocean Gray is a little lighter than Necromancer Cloak.
The same difference applies the other way round: Necromancer Cloak 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 Necromancer Cloak on the colour wheel See Ocean Gray on the colour wheel
All matches: Necromancer Cloak equivalents · Ocean Gray equivalents