Orange Tan vs Brethil Blush

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Brethil Blush is a little lighter than Orange Tan.

Can I use Brethil Blush instead of Orange Tan?

Usually, if you are not matching paint already on the model. Close match (ΔE 6). Brethil Blush is a little lighter than Orange Tan.

Can I use Orange Tan instead of Brethil Blush?

The same difference applies the other way round: Orange Tan is a little darker.

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.