Mechanicus Standard Grey vs Slate Grey

How close are they?

ΔE 10.6, fair: the same colour family, but not a straight swap. Our swatches for the two are almost the same.

Can I use Slate Grey instead of Mechanicus Standard Grey?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). The swatches are almost the same.

Can I use Mechanicus Standard Grey instead of Slate Grey?

The same difference applies the other way round.

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.