ΔE 14.2, fair: the same colour family, but not a straight swap. Sylvaneth Bark is a little darker, more muted, warmer than British Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Sylvaneth Bark is a little darker, more muted, warmer than British Brown.
The same difference applies the other way round: British Brown is a little lighter, 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 British Brown on the colour wheel See Sylvaneth Bark on the colour wheel
All matches: British Brown equivalents · Sylvaneth Bark equivalents