ΔE 17.0, loose: different enough that you should pick on purpose. Oxford Blue is more saturated, cooler than Nocturne Skin.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Oxford Blue is more saturated, cooler than Nocturne Skin.
The same difference applies the other way round: Nocturne Skin is 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.
See Nocturne Skin on the colour wheel See Oxford Blue on the colour wheel
All matches: Nocturne Skin equivalents · Oxford Blue equivalents