ΔE 9.7, close: similar, with a visible difference side by side. Flat Flesh is a little lighter, more muted, warmer than Raw Sienna.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Flat Flesh is a little lighter, more muted, warmer than Raw Sienna.
The same difference applies the other way round: Raw Sienna is a little darker, 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 Raw Sienna on the colour wheel See Flat Flesh on the colour wheel
All matches: Raw Sienna equivalents · Flat Flesh equivalents