ΔE 11.4, fair: the same colour family, but not a straight swap. German Red Brown is a little lighter, more muted, cooler than Russet Brown.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). German Red Brown is a little lighter, more muted, cooler than Russet Brown.
The same difference applies the other way round: Russet Brown is a little darker, more saturated, 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 Russet Brown on the colour wheel See German Red Brown on the colour wheel
All matches: Russet Brown equivalents · German Red Brown equivalents