ΔE 7.3, close: similar, with a visible difference side by side. IJN Ash Grey is a little lighter, cooler than Dirty Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). IJN Ash Grey is a little lighter, cooler than Dirty Grey.
The same difference applies the other way round: Dirty Grey is a little darker, 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.
See Dirty Grey on the colour wheel See IJN Ash Grey on the colour wheel
All matches: Dirty Grey equivalents · IJN Ash Grey equivalents