Cloudburst Blue vs Dark Blue Black

How close are they?

ΔE 23.7, loose: different enough that you should pick on purpose. Dark Blue Black is noticeably darker, more muted than Cloudburst Blue.

Can I use Dark Blue Black instead of Cloudburst Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Dark Blue Black is noticeably darker, more muted than Cloudburst Blue.

Can I use Cloudburst Blue instead of Dark Blue Black?

The same difference applies the other way round: Cloudburst Blue is noticeably lighter, 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.