ΔE 10.1, fair: the same colour family, but not a straight swap. Black Red is a little lighter, cooler than Walnut Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 10). Black Red is a little lighter, cooler than Walnut Brown.
The same difference applies the other way round: Walnut Brown is a little darker, 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 Walnut Brown on the colour wheel See Black Red on the colour wheel
All matches: Walnut Brown equivalents · Black Red equivalents