ΔE 7.0, close: similar, with a visible difference side by side. Walnut Brown is warmer than Onyx Skin. They are different kinds of paint: Army Painter Onyx Skin is an opaque base/layer paint and Green Stuff World Walnut Brown is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Walnut Brown is warmer than Onyx Skin. They are different kinds of paint.
The same difference applies the other way round: Onyx Skin is 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 Walnut Brown on the colour wheel
All matches: Onyx Skin equivalents · Walnut Brown equivalents