Metallic Blue vs Sapphire Blue

How close are they?

ΔE 15.3, loose: different enough that you should pick on purpose. Sapphire Blue is a little lighter, more muted, cooler than Metallic Blue.

Can I use Sapphire Blue instead of Metallic Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Sapphire Blue is a little lighter, more muted, cooler than Metallic Blue.

Can I use Metallic Blue instead of Sapphire Blue?

The same difference applies the other way round: Metallic Blue is a little darker, more saturated, 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.