ΔE 11.8, fair: the same colour family, but not a straight swap. Manganese Blue Hue is noticeably lighter, cooler than Ionic Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Manganese Blue Hue is noticeably lighter, cooler than Ionic Blue.
The same difference applies the other way round: Ionic Blue is noticeably darker, 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 Ionic Blue on the colour wheel See Manganese Blue Hue on the colour wheel
All matches: Ionic Blue equivalents · Manganese Blue Hue equivalents