Orruk Flesh vs Russian Green 1

How close are they?

ΔE 7.6, close: similar, with a visible difference side by side. Russian Green 1 is a little lighter than Orruk Flesh.

Can I use Russian Green 1 instead of Orruk Flesh?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Russian Green 1 is a little lighter than Orruk Flesh.

Can I use Orruk Flesh instead of Russian Green 1?

The same difference applies the other way round: Orruk Flesh 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.