Pallid Wych Flesh vs Pale Pink

How close are they?

ΔE 19.9, loose: different enough that you should pick on purpose. Pale Pink is a little lighter, more saturated than Pallid Wych Flesh.

Can I use Pale Pink instead of Pallid Wych Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Pale Pink is a little lighter, more saturated than Pallid Wych Flesh.

Can I use Pallid Wych Flesh instead of Pale Pink?

The same difference applies the other way round: Pallid Wych Flesh is a little darker, more muted.

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.