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