ΔE 11.1, fair: the same colour family, but not a straight swap. Royal Purple is noticeably darker, cooler than Octopus Purple.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Royal Purple is noticeably darker, cooler than Octopus Purple.
The same difference applies the other way round: Octopus Purple is noticeably 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 Octopus Purple on the colour wheel See Royal Purple on the colour wheel
All matches: Octopus Purple equivalents · Royal Purple equivalents