Human Flesh vs Shadow Flesh

How close are they?

ΔE 6.3, close: similar, with a visible difference side by side. Shadow Flesh is a little darker than Human Flesh.

Can I use Shadow Flesh instead of Human Flesh?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Shadow Flesh is a little darker than Human Flesh.

Can I use Human Flesh instead of Shadow Flesh?

The same difference applies the other way round: Human 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.