ΔE 11.9, fair: the same colour family, but not a straight swap. Royal Blue is noticeably 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 12). Royal Blue is noticeably darker, more muted than Witching Hour Blue.
The same difference applies the other way round: Witching Hour Blue is noticeably 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 Royal Blue on the colour wheel
All matches: Witching Hour Blue equivalents · Royal Blue equivalents