Power Blue vs Tidal Blue

How close are they?

ΔE 15.2, loose: different enough that you should pick on purpose. Tidal Blue is a little lighter, more muted, cooler than Power Blue.

Can I use Tidal Blue instead of Power Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 15). Tidal Blue is a little lighter, more muted, cooler than Power Blue.

Can I use Power Blue instead of Tidal Blue?

The same difference applies the other way round: Power Blue is a little darker, 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.