ΔE 9.2, close: similar, with a visible difference side by side. German Yellow is more saturated, cooler than Flak Gun Yellow.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). German Yellow is more saturated, cooler than Flak Gun Yellow.
The same difference applies the other way round: Flak Gun Yellow is 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.
See Flak Gun Yellow on the colour wheel See German Yellow on the colour wheel
All matches: Flak Gun Yellow equivalents · German Yellow equivalents