Slate Grey vs Black Grey RLM66

How close are they?

ΔE 10.7, fair: the same colour family, but not a straight swap. Black Grey RLM66 is a little lighter than Slate Grey.

Can I use Black Grey RLM66 instead of Slate Grey?

Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Black Grey RLM66 is a little lighter than Slate Grey.

Can I use Slate Grey instead of Black Grey RLM66?

The same difference applies the other way round: Slate Grey is a little 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.