ΔE 10.7, fair: the same colour family, but not a straight swap. Russet is a little darker, cooler than Ruddy Terra.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Russet is a little darker, cooler than Ruddy Terra.
The same difference applies the other way round: Ruddy Terra is a little lighter, 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 Ruddy Terra on the colour wheel See Russet on the colour wheel
All matches: Ruddy Terra equivalents · Russet equivalents