ΔE 13.8, fair: the same colour family, but not a straight swap. Naggaroth Night is more saturated, cooler than Space Purple.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Naggaroth Night is more saturated, cooler than Space Purple.
The same difference applies the other way round: Space Purple is more muted, 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 Space Purple on the colour wheel See Naggaroth Night on the colour wheel
All matches: Space Purple equivalents · Naggaroth Night equivalents