ΔE 9.6, close: similar, with a visible difference side by side. Brown FS30219 is a little lighter, more muted, warmer than Onyx Skin.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Brown FS30219 is a little lighter, more muted, warmer than Onyx Skin.
The same difference applies the other way round: Onyx Skin is a little darker, more saturated, cooler.
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 Onyx Skin on the colour wheel See Brown FS30219 on the colour wheel
All matches: Onyx Skin equivalents · Brown FS30219 equivalents