Desert Yellow vs Light Mustard Khaki

How close are they?

ΔE 8.2, close: similar, with a visible difference side by side. Light Mustard Khaki is cooler than Desert Yellow.

Can I use Light Mustard Khaki instead of Desert Yellow?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Light Mustard Khaki is cooler than Desert Yellow.

Can I use Desert Yellow instead of Light Mustard Khaki?

The same difference applies the other way round: Desert Yellow is 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.