Tidal Blue vs Blue Gray

How close are they?

ΔE 8.5, close: similar, with a visible difference side by side. Blue Gray is more muted, warmer than Tidal Blue.

Can I use Blue Gray instead of Tidal Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Blue Gray is more muted, warmer than Tidal Blue.

Can I use Tidal Blue instead of Blue Gray?

The same difference applies the other way round: Tidal Blue is 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.