Tomb King Tan vs Undead Flesh

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Undead Flesh is more saturated, cooler than Tomb King Tan.

Can I use Undead Flesh instead of Tomb King Tan?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Undead Flesh is more saturated, cooler than Tomb King Tan.

Can I use Tomb King Tan instead of Undead Flesh?

The same difference applies the other way round: Tomb King Tan is more muted, 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.