ΔE 9.6, close: similar, with a visible difference side by side. The Darkness is a little lighter, more muted than Night Blue INK. They are different kinds of paint: AK Interactive Night Blue INK is an ink, glaze or transparent paint and Army Painter The Darkness is an opaque base/layer paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). The Darkness is a little lighter, more muted than Night Blue INK. They are different kinds of paint.
The same difference applies the other way round: Night Blue INK is a little darker, 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 Night Blue INK on the colour wheel See The Darkness on the colour wheel
All matches: Night Blue INK equivalents · The Darkness equivalents