RAF Azure Blue vs Runic Cobalt

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Runic Cobalt is more muted, cooler than RAF Azure Blue.

Can I use Runic Cobalt instead of RAF Azure Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Runic Cobalt is more muted, cooler than RAF Azure Blue.

Can I use RAF Azure Blue instead of Runic Cobalt?

The same difference applies the other way round: RAF Azure Blue is more saturated, warmer.

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.