ΔE 11.8, fair: the same colour family, but not a straight swap. Russet is a little darker, cooler than Knight-Questor Flesh.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Russet is a little darker, cooler than Knight-Questor Flesh.
The same difference applies the other way round: Knight-Questor Flesh 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 Knight-Questor Flesh on the colour wheel See Russet on the colour wheel
All matches: Knight-Questor Flesh equivalents · Russet equivalents