ΔE 13.5, fair: the same colour family, but not a straight swap. Matt Black Primer is much 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 Matt Black Primer is a technical paint or medium, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Matt Black Primer is much more muted than Night Blue INK. They are different kinds of paint.
The same difference applies the other way round: Night Blue INK is much 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 Matt Black Primer on the colour wheel
All matches: Night Blue INK equivalents · Matt Black Primer equivalents