Brainmatter Beige vs Moon Mist Grey

How close are they?

ΔE 6.5, close: similar, with a visible difference side by side. Moon Mist Grey is a little darker than Brainmatter Beige.

Can I use Moon Mist Grey instead of Brainmatter Beige?

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

Can I use Brainmatter Beige instead of Moon Mist Grey?

The same difference applies the other way round: Brainmatter Beige is a little lighter.

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.