Aggaros Dunes vs Olive Yellow

How close are they?

ΔE 22.7, loose: different enough that you should pick on purpose. Olive Yellow is a little darker, much more saturated, cooler than Aggaros Dunes.

Can I use Olive Yellow instead of Aggaros Dunes?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Olive Yellow is a little darker, much more saturated, cooler than Aggaros Dunes.

Can I use Aggaros Dunes instead of Olive Yellow?

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