Ionic Blue vs Joridyn Turquoise

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Joridyn Turquoise is a little darker, more muted, cooler than Ionic Blue.

Can I use Joridyn Turquoise instead of Ionic Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Joridyn Turquoise is a little darker, more muted, cooler than Ionic Blue.

Can I use Ionic Blue instead of Joridyn Turquoise?

The same difference applies the other way round: Ionic Blue is a little lighter, more saturated, 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.