ΔE 13.2, fair: the same colour family, but not a straight swap. Night Sky is a little darker, cooler than King Purple.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Night Sky is a little darker, cooler than King Purple.
The same difference applies the other way round: King 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 King Purple on the colour wheel See Night Sky on the colour wheel
All matches: King Purple equivalents · Night Sky equivalents