ΔE 19.7, loose: different enough that you should pick on purpose. Purple is more muted, warmer than Cerulean Blue Deep.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Purple is more muted, warmer than Cerulean Blue Deep.
The same difference applies the other way round: Cerulean Blue Deep is more saturated, 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 Cerulean Blue Deep on the colour wheel See Purple on the colour wheel
All matches: Cerulean Blue Deep equivalents · Purple equivalents