Caledor Sky vs Brilliant Blue

How close are they?

ΔE 6.9, close: similar, with a visible difference side by side. Brilliant Blue is a little lighter than Caledor Sky.

Can I use Brilliant Blue instead of Caledor Sky?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Brilliant Blue is a little lighter than Caledor Sky.

Can I use Caledor Sky instead of Brilliant Blue?

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

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.