Omega Blue vs Hydra Turquoise

How close are they?

ΔE 25.0, loose: different enough that you should pick on purpose. Hydra Turquoise is noticeably darker, cooler than Omega Blue.

Can I use Hydra Turquoise instead of Omega Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 25). Hydra Turquoise is noticeably darker, cooler than Omega Blue.

Can I use Omega Blue instead of Hydra Turquoise?

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