ΔE 6.2, close: similar, with a visible difference side by side. Great Hall Grey is more saturated than Light Grey FS-35630.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Great Hall Grey is more saturated than Light Grey FS-35630.
The same difference applies the other way round: Light Grey FS-35630 is 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 Light Grey FS-35630 on the colour wheel See Great Hall Grey on the colour wheel
All matches: Light Grey FS-35630 equivalents · Great Hall Grey equivalents