ΔE 17.7, loose: different enough that you should pick on purpose. Moonstone Grey is a little lighter, much more muted than Light Feldgrau.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Moonstone Grey is a little lighter, much more muted than Light Feldgrau.
The same difference applies the other way round: Light Feldgrau is a little darker, 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.
See Light Feldgrau on the colour wheel See Moonstone Grey on the colour wheel
All matches: Light Feldgrau equivalents · Moonstone Grey equivalents