ΔE 8.6, close: similar, with a visible difference side by side. Flat Red is a little lighter than Alizarin Crimson Hue.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Flat Red is a little lighter than Alizarin Crimson Hue.
The same difference applies the other way round: Alizarin Crimson Hue is a little darker.
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 Alizarin Crimson Hue on the colour wheel See Flat Red on the colour wheel
All matches: Alizarin Crimson Hue equivalents · Flat Red equivalents