Arid Earth vs Lilith Yellow

How close are they?

ΔE 15.1, loose: different enough that you should pick on purpose. Lilith Yellow is a little darker, more saturated than Arid Earth.

Can I use Lilith Yellow instead of Arid Earth?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Lilith Yellow is a little darker, more saturated than Arid Earth.

Can I use Arid Earth instead of Lilith Yellow?

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

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.