ΔE 9.8, close: similar, with a visible difference side by side. Scarlet is more saturated, cooler than Carmine.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Scarlet is more saturated, cooler than Carmine.
The same difference applies the other way round: Carmine is more muted, 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 Carmine on the colour wheel See Scarlet on the colour wheel
All matches: Carmine equivalents · Scarlet equivalents