Light Orange vs Brethil Blush

How close are they?

ΔE 9.3, close: similar, with a visible difference side by side. Brethil Blush is a little darker, more muted than Light Orange.

Can I use Brethil Blush instead of Light Orange?

Usually, if you are not matching paint already on the model. Close match (ΔE 9). Brethil Blush is a little darker, more muted than Light Orange.

Can I use Light Orange instead of Brethil Blush?

The same difference applies the other way round: Light 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.