Caledor Sky vs Blue Base

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Blue Base is more muted, warmer than Caledor Sky.

Can I use Blue Base instead of Caledor Sky?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Blue Base is more muted, warmer than Caledor Sky.

Can I use Caledor Sky instead of Blue Base?

The same difference applies the other way round: Caledor Sky 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.