Mid Brown vs Mortarion Grime

How close are they?

ΔE 20.2, loose: different enough that you should pick on purpose. Mortarion Grime is a little lighter, more muted, cooler than Mid Brown.

Can I use Mortarion Grime instead of Mid Brown?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 20). Mortarion Grime is a little lighter, more muted, cooler than Mid Brown.

Can I use Mid Brown instead of Mortarion Grime?

The same difference applies the other way round: Mid Brown is a little darker, more saturated, warmer.

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.