ΔE 23.1, loose: different enough that you should pick on purpose. Cerulean Blue, Chromium is a little darker, much more saturated, warmer than Ionic Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Cerulean Blue, Chromium is a little darker, much more saturated, warmer than Ionic Blue.
The same difference applies the other way round: Ionic Blue is a little lighter, much more muted, 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 Ionic Blue on the colour wheel See Cerulean Blue, Chromium on the colour wheel
All matches: Ionic Blue equivalents · Cerulean Blue, Chromium equivalents