Calth Blue Clear vs Blueberry

How close are they?

ΔE 17.3, loose: different enough that you should pick on purpose. Blueberry is a little lighter, warmer than Calth Blue Clear.

Can I use Blueberry instead of Calth Blue Clear?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Blueberry is a little lighter, warmer than Calth Blue Clear.

Can I use Calth Blue Clear instead of Blueberry?

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