Petroleum Gray vs IJN Black Green

How close are they?

ΔE 7.1, close: similar, with a visible difference side by side. IJN Black Green is a little lighter, more saturated than Petroleum Gray.

Can I use IJN Black Green instead of Petroleum Gray?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). IJN Black Green is a little lighter, more saturated than Petroleum Gray.

Can I use Petroleum Gray instead of IJN Black Green?

The same difference applies the other way round: Petroleum Gray is a little 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.