ΔE 6.3, close: similar, with a visible difference side by side. Flat Earth is warmer than Russet Shadow.
Usually, if you are not matching paint already on the model. Close match (ΔE 6). Flat Earth is warmer than Russet Shadow.
The same difference applies the other way round: Russet Shadow is 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 Russet Shadow on the colour wheel See Flat Earth on the colour wheel
All matches: Russet Shadow equivalents · Flat Earth equivalents