Plague Yellow vs Sand Yellow

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Sand Yellow is a little lighter than Plague Yellow.

Can I use Sand Yellow instead of Plague Yellow?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Sand Yellow is a little lighter than Plague Yellow.

Can I use Plague Yellow instead of Sand Yellow?

The same difference applies the other way round: Plague Yellow is a little darker.

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.