Terradon Turquoise vs Leviathan Blue

How close are they?

ΔE 22.8, loose: different enough that you should pick on purpose. Leviathan Blue is noticeably darker, more muted, cooler than Terradon Turquoise.

Can I use Leviathan Blue instead of Terradon Turquoise?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 23). Leviathan Blue is noticeably darker, more muted, cooler than Terradon Turquoise.

Can I use Terradon Turquoise instead of Leviathan Blue?

The same difference applies the other way round: Terradon Turquoise is noticeably 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.