ΔE 12.3, fair: the same colour family, but not a straight swap. Dark Gray is a little darker, more muted, cooler than Russ Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Dark Gray is a little darker, more muted, cooler than Russ Grey.
The same difference applies the other way round: Russ Grey is a little lighter, 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.
See Russ Grey on the colour wheel See Dark Gray on the colour wheel
All matches: Russ Grey equivalents · Dark Gray equivalents