Light Metallic Blue vs Sapphire Blue

How close are they?

ΔE 23.0, loose: different enough that you should pick on purpose. Sapphire Blue is noticeably lighter, warmer than Light Metallic Blue.

Can I use Sapphire Blue instead of Light Metallic Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Sapphire Blue is noticeably lighter, warmer than Light Metallic Blue.

Can I use Light Metallic Blue instead of Sapphire Blue?

The same difference applies the other way round: Light Metallic Blue is noticeably darker, 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.