Caledor Sky vs Cobalt Blue

How close are they?

ΔE 18.1, loose: different enough that you should pick on purpose. Cobalt Blue is a little lighter, much more saturated, warmer than Caledor Sky.

Can I use Cobalt Blue instead of Caledor Sky?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Cobalt Blue is a little lighter, much more saturated, warmer than Caledor Sky.

Can I use Caledor Sky instead of Cobalt Blue?

The same difference applies the other way round: Caledor Sky is a little darker, much more muted, 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.