ΔE 6.9, close: similar, with a visible difference side by side. IJN Medium Grey is a little darker, more saturated than Seal Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). IJN Medium Grey is a little darker, more saturated than Seal Grey.
The same difference applies the other way round: Seal Grey is a little lighter, 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.
See Seal Grey on the colour wheel See IJN Medium Grey on the colour wheel
All matches: Seal Grey equivalents · IJN Medium Grey equivalents