ΔE 14.8, fair: the same colour family, but not a straight swap. Oxford Blue is a little lighter, much more muted, cooler than Naggaroth Night.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Oxford Blue is a little lighter, much more muted, cooler than Naggaroth Night.
The same difference applies the other way round: Naggaroth Night is a little darker, much 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 Oxford Blue on the colour wheel
All matches: Naggaroth Night equivalents · Oxford Blue equivalents