Purple Tone vs Aether Blue

How close are they?

ΔE 39.9, loose: different enough that you should pick on purpose. Aether Blue is noticeably lighter, much more muted, cooler than Purple Tone.

Can I use Aether Blue instead of Purple Tone?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 40). Aether Blue is noticeably lighter, much more muted, cooler than Purple Tone.

Can I use Purple Tone instead of Aether Blue?

The same difference applies the other way round: Purple Tone is noticeably darker, much 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.