RAF Cockpit Grey-Green vs IJN Ash Grey

How close are they?

ΔE 7.9, close: similar, with a visible difference side by side. IJN Ash Grey is more muted, warmer than RAF Cockpit Grey-Green.

Can I use IJN Ash Grey instead of RAF Cockpit Grey-Green?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). IJN Ash Grey is more muted, warmer than RAF Cockpit Grey-Green.

Can I use RAF Cockpit Grey-Green instead of IJN Ash Grey?

The same difference applies the other way round: RAF Cockpit Grey-Green 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.