Overlord Olive vs Dark Green RLM71

How close are they?

ΔE 8.6, close: similar, with a visible difference side by side. Dark Green RLM71 is a little lighter, cooler than Overlord Olive.

Can I use Dark Green RLM71 instead of Overlord Olive?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Dark Green RLM71 is a little lighter, cooler than Overlord Olive.

Can I use Overlord Olive instead of Dark Green RLM71?

The same difference applies the other way round: Overlord Olive is a little darker, warmer.

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.