Shadow Flesh vs Bloodreaver Flesh

How close are they?

ΔE 8.7, close: similar, with a visible difference side by side. Bloodreaver Flesh is a little darker, warmer than Shadow Flesh.

Can I use Bloodreaver Flesh instead of Shadow Flesh?

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

Can I use Shadow Flesh instead of Bloodreaver Flesh?

The same difference applies the other way round: Shadow Flesh 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.