Bright Green vs Orruk Flesh

How close are they?

ΔE 6.1, close: similar, with a visible difference side by side. Orruk Flesh is a little darker than Bright Green.

Can I use Orruk Flesh instead of Bright Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Orruk Flesh is a little darker than Bright Green.

Can I use Bright Green instead of Orruk Flesh?

The same difference applies the other way round: Bright Green is a little lighter.

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.