Imp Yellow vs Desert Sand

How close are they?

ΔE 16.1, loose: different enough that you should pick on purpose. Desert Sand is a little lighter, more muted, cooler than Imp Yellow.

Can I use Desert Sand instead of Imp Yellow?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Desert Sand is a little lighter, more muted, cooler than Imp Yellow.

Can I use Imp Yellow instead of Desert Sand?

The same difference applies the other way round: Imp Yellow is a little darker, more saturated, 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.