Aether Blue vs Umber Wash

How close are they?

ΔE 35.8, loose: different enough that you should pick on purpose. Umber Wash is much more muted, warmer than Aether Blue.

Can I use Umber Wash instead of Aether Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 36). Umber Wash is much more muted, warmer than Aether Blue.

Can I use Aether Blue instead of Umber Wash?

The same difference applies the other way round: Aether Blue is much more saturated, 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.