Bright Sapphire vs Cobalt Teal

How close are they?

ΔE 22.9, loose: different enough that you should pick on purpose. Cobalt Teal is a little darker, more saturated, warmer than Bright Sapphire.

Can I use Cobalt Teal instead of Bright Sapphire?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Cobalt Teal is a little darker, more saturated, warmer than Bright Sapphire.

Can I use Bright Sapphire instead of Cobalt Teal?

The same difference applies the other way round: Bright Sapphire is a little lighter, more muted, 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.