Ochre Clay vs Aggaros Dunes

How close are they?

ΔE 19.4, loose: different enough that you should pick on purpose. Aggaros Dunes is much more muted, warmer than Ochre Clay.

Can I use Aggaros Dunes instead of Ochre Clay?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Aggaros Dunes is much more muted, warmer than Ochre Clay.

Can I use Ochre Clay instead of Aggaros Dunes?

The same difference applies the other way round: Ochre Clay 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.