Ensign Blue vs Azurite Hue

How close are they?

ΔE 19.1, loose: different enough that you should pick on purpose. Azurite Hue is noticeably lighter, more saturated than Ensign Blue.

Can I use Azurite Hue instead of Ensign Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Azurite Hue is noticeably lighter, more saturated than Ensign Blue.

Can I use Ensign Blue instead of Azurite Hue?

The same difference applies the other way round: Ensign Blue is noticeably darker, more muted.

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.