Arid Earth vs Thrall Flesh

How close are they?

ΔE 15.5, loose: different enough that you should pick on purpose. Thrall Flesh is a little darker, cooler than Arid Earth.

Can I use Thrall Flesh instead of Arid Earth?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Thrall Flesh is a little darker, cooler than Arid Earth.

Can I use Arid Earth instead of Thrall Flesh?

The same difference applies the other way round: Arid Earth is a little lighter, 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.