Dark Green Nakajima vs Olive Grey

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Olive Grey is more muted, warmer than Dark Green Nakajima.

Can I use Olive Grey instead of Dark Green Nakajima?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Olive Grey is more muted, warmer than Dark Green Nakajima.

Can I use Dark Green Nakajima instead of Olive Grey?

The same difference applies the other way round: Dark Green Nakajima is more saturated, cooler.

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.