Tombstone Yellow vs Mid Mustard Khaki

How close are they?

ΔE 9.2, close: similar, with a visible difference side by side. Mid Mustard Khaki is a little darker, more saturated than Tombstone Yellow.

Can I use Mid Mustard Khaki instead of Tombstone Yellow?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Mid Mustard Khaki is a little darker, more saturated than Tombstone Yellow.

Can I use Tombstone Yellow instead of Mid Mustard Khaki?

The same difference applies the other way round: Tombstone Yellow is a little lighter, 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.