ΔE 7.7, close: similar, with a visible difference side by side. Flat Green is a little darker, warmer than Light Feldgrau.
Usually, if you are not matching paint already on the model. Close match (ΔE 8). Flat Green is a little darker, warmer than Light Feldgrau.
The same difference applies the other way round: Light Feldgrau is a little lighter, 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 Light Feldgrau on the colour wheel See Flat Green on the colour wheel
All matches: Light Feldgrau equivalents · Flat Green equivalents