Vivid Flesh vs Faded Red

How close are they?

ΔE 8.7, close: similar, with a visible difference side by side. Faded Red is a little darker than Vivid Flesh.

Can I use Faded Red instead of Vivid Flesh?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Faded Red is a little darker than Vivid Flesh.

Can I use Vivid Flesh instead of Faded Red?

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

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.