ΔE 15.5, loose: different enough that you should pick on purpose. Vampiric Purple is more saturated, warmer than Indigo Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Vampiric Purple is more saturated, warmer than Indigo Blue.
The same difference applies the other way round: Indigo Blue is more muted, 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 Indigo Blue on the colour wheel See Vampiric Purple on the colour wheel
All matches: Indigo Blue equivalents · Vampiric Purple equivalents