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