Ember Orange vs Parasite Brown

How close are they?

ΔE 9.9, close: similar, with a visible difference side by side. Parasite Brown is a little darker, more muted than Ember Orange.

Can I use Parasite Brown instead of Ember Orange?

Usually, if you are not matching paint already on the model. Close match (ΔE 10). Parasite Brown is a little darker, more muted than Ember Orange.

Can I use Ember Orange instead of Parasite Brown?

The same difference applies the other way round: Ember Orange is a little lighter, more saturated.

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.