Hydra Turquoise vs Cloud Sea

How close are they?

ΔE 15.2, loose: different enough that you should pick on purpose. Cloud Sea is noticeably darker, more muted, warmer than Hydra Turquoise.

Can I use Cloud Sea instead of Hydra Turquoise?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Cloud Sea is noticeably darker, more muted, warmer than Hydra Turquoise.

Can I use Hydra Turquoise instead of Cloud Sea?

The same difference applies the other way round: Hydra Turquoise is noticeably lighter, more saturated, 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.