Archangel Red vs Ember Orange

How close are they?

ΔE 9.7, close: similar, with a visible difference side by side. Ember Orange is a little lighter, more saturated than Archangel Red.

Can I use Ember Orange instead of Archangel Red?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Ember Orange is a little lighter, more saturated than Archangel Red.

Can I use Archangel Red instead of Ember Orange?

The same difference applies the other way round: Archangel Red is a little darker, 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.