Ochre Green vs Tan Earth

How close are they?

ΔE 6.2, close: similar, with a visible difference side by side. Tan Earth is a little lighter, more muted than Ochre Green.

Can I use Tan Earth instead of Ochre Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Tan Earth is a little lighter, more muted than Ochre Green.

Can I use Ochre Green instead of Tan Earth?

The same difference applies the other way round: Ochre Green is a little darker, more saturated.

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.