ΔE 8.0, close: similar, with a visible difference side by side. Sombre Grey is a little darker, more saturated, warmer than Medium Gray.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Sombre Grey is a little darker, more saturated, warmer than Medium Gray.
The same difference applies the other way round: Medium Gray is a little lighter, more muted, 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.
See Medium Gray on the colour wheel See Sombre Grey on the colour wheel
All matches: Medium Gray equivalents · Sombre Grey equivalents