ΔE 12.7, fair: the same colour family, but not a straight swap. AMT-1 Lt. Grey. Brown is noticeably lighter than Brown Grey.
Can I use AMT-1 Lt. Grey. Brown instead of Brown Grey?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). AMT-1 Lt. Grey. Brown is noticeably lighter than Brown Grey.
Can I use Brown Grey instead of AMT-1 Lt. Grey. Brown?
The same difference applies the other way round: Brown Grey is noticeably 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.