Baharroth Blue vs Grey Blue

How close are they?

ΔE 17.2, loose: different enough that you should pick on purpose. Grey Blue is much more muted, warmer than Baharroth Blue.

Can I use Grey Blue instead of Baharroth Blue?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Grey Blue is much more muted, warmer than Baharroth Blue.

Can I use Baharroth Blue instead of Grey Blue?

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