ΔE 10.9, fair: the same colour family, but not a straight swap. Flanker Light Blue is a little darker, warmer than Ion Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Flanker Light Blue is a little darker, warmer than Ion Blue.
The same difference applies the other way round: Ion Blue is a little lighter, 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 Ion Blue on the colour wheel See Flanker Light Blue on the colour wheel
All matches: Ion Blue equivalents · Flanker Light Blue equivalents