RAF Azure Blue vs Elfic Blue

How close are they?

ΔE 7.5, close: similar, with a visible difference side by side. Elfic Blue is more saturated than RAF Azure Blue.

Can I use Elfic Blue instead of RAF Azure Blue?

Usually, if you are not matching paint already on the model. Close match (ΔE 8). Elfic Blue is more saturated than RAF Azure Blue.

Can I use RAF Azure Blue instead of Elfic Blue?

The same difference applies the other way round: RAF Azure Blue is more muted.

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.