Dark Marine Green vs Orruk Flesh

How close are they?

ΔE 17.4, loose: different enough that you should pick on purpose. Orruk Flesh is noticeably lighter, more saturated than Dark Marine Green.

Can I use Orruk Flesh instead of Dark Marine Green?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Orruk Flesh is noticeably lighter, more saturated than Dark Marine Green.

Can I use Dark Marine Green instead of Orruk Flesh?

The same difference applies the other way round: Dark Marine Green is noticeably darker, more muted.

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.