Flayed One Flesh vs Elven Flesh

How close are they?

ΔE 19.2, loose: different enough that you should pick on purpose. Elven Flesh is a little lighter, much more saturated, cooler than Flayed One Flesh.

Can I use Elven Flesh instead of Flayed One Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Elven Flesh is a little lighter, much more saturated, cooler than Flayed One Flesh.

Can I use Flayed One Flesh instead of Elven Flesh?

The same difference applies the other way round: Flayed One Flesh is a little darker, much more muted, 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.