ΔE 17.5, loose: different enough that you should pick on purpose. Cerulean Blue Deep is noticeably lighter, more saturated, cooler than Broodmother Purple.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Cerulean Blue Deep is noticeably lighter, more saturated, cooler than Broodmother Purple.
The same difference applies the other way round: Broodmother Purple is noticeably darker, more muted, 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 Broodmother Purple on the colour wheel See Cerulean Blue Deep on the colour wheel
All matches: Broodmother Purple equivalents · Cerulean Blue Deep equivalents