ΔE 20.4, loose: different enough that you should pick on purpose. Marine Blue is noticeably lighter, more muted, cooler than Naggaroth Night.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Marine Blue is noticeably lighter, more muted, cooler than Naggaroth Night.
The same difference applies the other way round: Naggaroth Night is noticeably darker, more saturated, warmer.
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 Naggaroth Night on the colour wheel See Marine Blue on the colour wheel
All matches: Naggaroth Night equivalents · Marine Blue equivalents