ΔE 12.3, fair: the same colour family, but not a straight swap. Cygnar Blue Base is a little darker, cooler than Alien Purple.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Cygnar Blue Base is a little darker, cooler than Alien Purple.
The same difference applies the other way round: Alien Purple is a little lighter, 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 Cygnar Blue Base on the colour wheel
All matches: Alien Purple equivalents · Cygnar Blue Base equivalents