Green Uniform Base vs Midnight Olive

How close are they?

ΔE 8.8, close: similar, with a visible difference side by side. Midnight Olive is more muted than Green Uniform Base.

Can I use Midnight Olive instead of Green Uniform Base?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Midnight Olive is more muted than Green Uniform Base.

Can I use Green Uniform Base instead of Midnight Olive?

The same difference applies the other way round: Green Uniform Base is more saturated.

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.