ΔE 22.2, loose: different enough that you should pick on purpose. Ink Violet is a little darker, much more saturated, warmer than Night Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Ink Violet is a little darker, much more saturated, warmer than Night Blue.
The same difference applies the other way round: Night Blue is a little lighter, much more muted, cooler.
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 on the colour wheel See Ink Violet on the colour wheel
All matches: Night Blue equivalents · Ink Violet equivalents