ΔE 9.5, close: similar, with a visible difference side by side. Infantry Blue is a little darker, more saturated than Strap Grey.
Usually, if you are not matching paint already on the model. Close match (ΔE 9). Infantry Blue is a little darker, more saturated than Strap Grey.
The same difference applies the other way round: Strap Grey is a little lighter, more muted.
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 Strap Grey on the colour wheel See Infantry Blue on the colour wheel
All matches: Strap Grey equivalents · Infantry Blue equivalents