ΔE 14.6, fair: the same colour family, but not a straight swap. Administratum Grey is much more muted than Light Feldgrau.
Can I use Administratum Grey instead of Light Feldgrau?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Administratum Grey is much more muted than Light Feldgrau.
Can I use Light Feldgrau instead of Administratum Grey?
The same difference applies the other way round: Light Feldgrau is much more saturated.
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.