Caledor Sky vs Ultramarine Highlight

How close are they?

ΔE 6.1, close: similar, with a visible difference side by side. Ultramarine Highlight is a little lighter than Caledor Sky.

Can I use Ultramarine Highlight instead of Caledor Sky?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Ultramarine Highlight is a little lighter than Caledor Sky.

Can I use Caledor Sky instead of Ultramarine Highlight?

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.