Sand Grey vs Mid Mustard Khaki

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Mid Mustard Khaki is a little lighter than Sand Grey.

Can I use Mid Mustard Khaki instead of Sand Grey?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Mid Mustard Khaki is a little lighter than Sand Grey.

Can I use Sand Grey instead of Mid Mustard Khaki?

The same difference applies the other way round: Sand Grey 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.