ΔE 9.5, close: similar, with a visible difference side by side. Prussian Blue is a little lighter, more saturated, cooler than Blue FS15050.
Usually, if you are not matching paint already on the model. Close match (ΔE 10). Prussian Blue is a little lighter, more saturated, cooler than Blue FS15050.
The same difference applies the other way round: Blue FS15050 is a little darker, 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 Blue FS15050 on the colour wheel See Prussian Blue on the colour wheel
All matches: Blue FS15050 equivalents · Prussian Blue equivalents