ΔE 9.0, close: similar, with a visible difference side by side. Barbarian Skin is a little darker, more saturated than Buff.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Barbarian Skin is a little darker, more saturated than Buff.
The same difference applies the other way round: Buff is a little lighter, 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.
See Buff on the colour wheel See Barbarian Skin on the colour wheel
All matches: Buff equivalents · Barbarian Skin equivalents