Tidal Wave vs Asurmen Blue

How close are they?

ΔE 18.7, loose: different enough that you should pick on purpose. Asurmen Blue is noticeably darker, more muted, warmer than Tidal Wave.

Can I use Asurmen Blue instead of Tidal Wave?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 19). Asurmen Blue is noticeably darker, more muted, warmer than Tidal Wave.

Can I use Tidal Wave instead of Asurmen Blue?

The same difference applies the other way round: Tidal Wave 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.