Tan Earth vs Gorthor Brown

How close are they?

ΔE 6.4, close: similar, with a visible difference side by side. Gorthor Brown is a little darker, warmer than Tan Earth.

Can I use Gorthor Brown instead of Tan Earth?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Gorthor Brown is a little darker, warmer than Tan Earth.

Can I use Tan Earth instead of Gorthor Brown?

The same difference applies the other way round: Tan Earth is a little lighter, cooler.

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.