Agrax Earthshade vs Tempest Blue Wash

How close are they?

ΔE 28.7, loose: different enough that you should pick on purpose. Tempest Blue Wash is noticeably lighter, cooler than Agrax Earthshade.

Can I use Tempest Blue Wash instead of Agrax Earthshade?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 29). Tempest Blue Wash is noticeably lighter, cooler than Agrax Earthshade.

Can I use Agrax Earthshade instead of Tempest Blue Wash?

The same difference applies the other way round: Agrax Earthshade is noticeably darker, 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.