ΔE 12.6, fair: the same colour family, but not a straight swap. Ghost Blue is a little lighter, more muted, cooler than Alien Purple.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Ghost Blue is a little lighter, more muted, cooler than Alien Purple.
The same difference applies the other way round: Alien Purple is a little darker, 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 Alien Purple on the colour wheel See Ghost Blue on the colour wheel
All matches: Alien Purple equivalents · Ghost Blue equivalents