ΔE 6.6, close: similar, with a visible difference side by side. Neutral Grey is a little lighter than Light Gray (IJN).
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Neutral Grey is a little lighter than Light Gray (IJN).
The same difference applies the other way round: Light Gray (IJN) is a little darker.
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 Light Gray (IJN) on the colour wheel See Neutral Grey on the colour wheel
All matches: Light Gray (IJN) equivalents · Neutral Grey equivalents