Light Pink Flesh vs Pallid Wych Flesh

How close are they?

ΔE 16.8, loose: different enough that you should pick on purpose. Pallid Wych Flesh is a little darker, more muted, cooler than Light Pink Flesh.

Can I use Pallid Wych Flesh instead of Light Pink Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Pallid Wych Flesh is a little darker, more muted, cooler than Light Pink Flesh.

Can I use Light Pink Flesh instead of Pallid Wych Flesh?

The same difference applies the other way round: Light Pink Flesh is a little lighter, more saturated, 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.