Caribbean Ocean vs Nighthaunt Gloom

How close are they?

ΔE 15.9, loose: different enough that you should pick on purpose. Nighthaunt Gloom is a little darker, more muted, cooler than Caribbean Ocean.

Can I use Nighthaunt Gloom instead of Caribbean Ocean?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Nighthaunt Gloom is a little darker, more muted, cooler than Caribbean Ocean.

Can I use Caribbean Ocean instead of Nighthaunt Gloom?

The same difference applies the other way round: Caribbean Ocean is a little lighter, 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.