Caledor Sky vs Braineater Azure

How close are they?

ΔE 15.9, loose: different enough that you should pick on purpose. Braineater Azure is noticeably lighter, warmer than Caledor Sky.

Can I use Braineater Azure instead of Caledor Sky?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Braineater Azure is noticeably lighter, warmer than Caledor Sky.

Can I use Caledor Sky instead of Braineater Azure?

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