ΔE 31.0, loose: different enough that you should pick on purpose. Violet Vamp is noticeably darker, much more muted, warmer than Neptune's Fury.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 31). Violet Vamp is noticeably darker, much more muted, warmer than Neptune's Fury.
The same difference applies the other way round: Neptune's Fury is noticeably lighter, much more saturated, 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 Neptune's Fury on the colour wheel See Violet Vamp on the colour wheel
All matches: Neptune's Fury equivalents · Violet Vamp equivalents