Necrotic Flesh vs Sky BS381C/210

How close are they?

ΔE 7.0, close: similar, with a visible difference side by side. Sky BS381C/210 is a little lighter, cooler than Necrotic Flesh.

Can I use Sky BS381C/210 instead of Necrotic Flesh?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Sky BS381C/210 is a little lighter, cooler than Necrotic Flesh.

Can I use Necrotic Flesh instead of Sky BS381C/210?

The same difference applies the other way round: Necrotic Flesh is a little darker, 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.