Vivid Flesh vs German Orange

How close are they?

ΔE 9.8, close: similar, with a visible difference side by side. German Orange is a little darker, more muted than Vivid Flesh.

Can I use German Orange instead of Vivid Flesh?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). German Orange is a little darker, more muted than Vivid Flesh.

Can I use Vivid Flesh instead of German Orange?

The same difference applies the other way round: Vivid Flesh is a little lighter, 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.