Ivory vs Brainmatter Beige

How close are they?

ΔE 6.7, close: similar, with a visible difference side by side. Brainmatter Beige is a little darker, more muted than Ivory.

Can I use Brainmatter Beige instead of Ivory?

Usually, if you are not matching paint already on the model. Close match (ΔE 7). Brainmatter Beige is a little darker, more muted than Ivory.

Can I use Ivory instead of Brainmatter Beige?

The same difference applies the other way round: Ivory 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.