ΔE 14.8, fair: the same colour family, but not a straight swap. IDF Blue is noticeably darker, cooler than Grey Blue.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). IDF Blue is noticeably darker, cooler than Grey Blue.
The same difference applies the other way round: Grey Blue is noticeably lighter, 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 Grey Blue on the colour wheel See IDF Blue on the colour wheel
All matches: Grey Blue equivalents · IDF Blue equivalents