ΔE 23.0, loose: different enough that you should pick on purpose. Spectral Purple is noticeably lighter, warmer than Diabolic Plum.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Spectral Purple is noticeably lighter, warmer than Diabolic Plum.
The same difference applies the other way round: Diabolic Plum is noticeably darker, cooler.
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 Diabolic Plum on the colour wheel See Spectral Purple on the colour wheel
All matches: Diabolic Plum equivalents · Spectral Purple equivalents