ΔE 11.0, fair: the same colour family, but not a straight swap. IDF Blue is more muted than Temple Guard Blue.
Can I use IDF Blue instead of Temple Guard Blue?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). IDF Blue is more muted than Temple Guard Blue.
Can I use Temple Guard Blue instead of IDF Blue?
The same difference applies the other way round: Temple Guard Blue is more saturated.
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.