ΔE 18.9, loose: different enough that you should pick on purpose. Ion Blue is a little lighter, more muted than Augur Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Ion Blue is a little lighter, more muted than Augur Blue.
The same difference applies the other way round: Augur Blue is a little darker, more saturated.
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 Augur Blue on the colour wheel See Ion Blue on the colour wheel
All matches: Augur Blue equivalents · Ion Blue equivalents