ΔE 9.7, close: similar, with a visible difference side by side. Medium Gray is more muted, warmer than Pastel Blue.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Medium Gray is more muted, warmer than Pastel Blue.
The same difference applies the other way round: Pastel Blue 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.
See Pastel Blue on the colour wheel See Medium Gray on the colour wheel
All matches: Pastel Blue equivalents · Medium Gray equivalents