Soulblight Grey vs Aether Blue

How close are they?

ΔE 27.0, loose: different enough that you should pick on purpose. Aether Blue is a little darker, much more saturated than Soulblight Grey.

Can I use Aether Blue instead of Soulblight Grey?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Aether Blue is a little darker, much more saturated than Soulblight Grey.

Can I use Soulblight Grey instead of Aether Blue?

The same difference applies the other way round: Soulblight Grey is a little lighter, much more muted.

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.