Grey Blue vs UK Azure Blue

How close are they?

ΔE 8.6, close: similar, with a visible difference side by side. UK Azure Blue is a little darker, more saturated, warmer than Grey Blue.

Can I use UK Azure Blue instead of Grey Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). UK Azure Blue is a little darker, more saturated, warmer than Grey Blue.

Can I use Grey Blue instead of UK Azure Blue?

The same difference applies the other way round: Grey Blue is a little lighter, more muted, 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.