Noble Skin vs Willow Bark

How close are they?

ΔE 16.2, loose: different enough that you should pick on purpose. Willow Bark is noticeably darker, more muted than Noble Skin.

Can I use Willow Bark instead of Noble Skin?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Willow Bark is noticeably darker, more muted than Noble Skin.

Can I use Noble Skin instead of Willow Bark?

The same difference applies the other way round: Noble Skin is noticeably lighter, more saturated.

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.