A-18f Light Grey-Blue vs Light Feldgrau

How close are they?

ΔE 8.1, close: similar, with a visible difference side by side. Light Feldgrau is a little darker, warmer than A-18f Light Grey-Blue.

Can I use Light Feldgrau instead of A-18f Light Grey-Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Light Feldgrau is a little darker, warmer than A-18f Light Grey-Blue.

Can I use A-18f Light Grey-Blue instead of Light Feldgrau?

The same difference applies the other way round: A-18f Light Grey-Blue 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.