Dark Sand vs Zamesi Desert

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Zamesi Desert is a little darker, much more saturated than Dark Sand.

Can I use Zamesi Desert instead of Dark Sand?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Zamesi Desert is a little darker, much more saturated than Dark Sand.

Can I use Dark Sand instead of Zamesi Desert?

The same difference applies the other way round: Dark Sand is a little lighter, much 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.