ΔE 10.5, fair: the same colour family, but not a straight swap. Skin Tone is more muted, cooler than Flat Flesh.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Skin Tone is more muted, cooler than Flat Flesh.
The same difference applies the other way round: Flat Flesh is 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 Flat Flesh on the colour wheel See Skin Tone on the colour wheel
All matches: Flat Flesh equivalents · Skin Tone equivalents