ΔE 11.4, fair: the same colour family, but not a straight swap. Imperial Blue is a little darker, more muted than Witching Hour Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Imperial Blue is a little darker, more muted than Witching Hour Blue.
The same difference applies the other way round: Witching Hour Blue is a little lighter, more saturated.
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 Witching Hour Blue on the colour wheel See Imperial Blue on the colour wheel
All matches: Witching Hour Blue equivalents · Imperial Blue equivalents