Commando Green vs Deep Ocean

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Deep Ocean is more saturated, cooler than Commando Green.

Can I use Deep Ocean instead of Commando Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Deep Ocean is more saturated, cooler than Commando Green.

Can I use Commando Green instead of Deep Ocean?

The same difference applies the other way round: Commando Green is more muted, 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.