ΔE 11.0, fair: the same colour family, but not a straight swap. Gorthor Brown is more saturated, warmer than Onyx Skin.
✓ Army Painter Fanatic conversion chart lists these two as equivalents.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Gorthor Brown is more saturated, warmer than Onyx Skin.
The same difference applies the other way round: Onyx Skin is more muted, 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 Gorthor Brown on the colour wheel
All matches: Onyx Skin equivalents · Gorthor Brown equivalents