ΔE 18.0, loose: different enough that you should pick on purpose. Wraithbone is noticeably darker, cooler than Opal Skin.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Wraithbone is noticeably darker, cooler than Opal Skin.
The same difference applies the other way round: Opal Skin is noticeably lighter, 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.
See Opal Skin on the colour wheel See Wraithbone on the colour wheel
All matches: Opal Skin equivalents · Wraithbone equivalents