Caledor Sky vs Summersea Blue

How close are they?

ΔE 8.5, close: similar, with a visible difference side by side. Summersea Blue is a little lighter, more saturated than Caledor Sky.

Can I use Summersea Blue instead of Caledor Sky?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Summersea Blue is a little lighter, more saturated than Caledor Sky.

Can I use Caledor Sky instead of Summersea Blue?

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

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.