Light Feldgrau vs Morning Sky

How close are they?

ΔE 16.9, loose: different enough that you should pick on purpose. Morning Sky is a little darker, more saturated, cooler than Light Feldgrau.

Can I use Morning Sky instead of Light Feldgrau?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Morning Sky is a little darker, more saturated, cooler than Light Feldgrau.

Can I use Light Feldgrau instead of Morning Sky?

The same difference applies the other way round: Light Feldgrau is a little lighter, more muted, warmer.

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.