ΔE 11.7, fair: the same colour family, but not a straight swap. Steel Grey is more saturated, cooler than Smoke Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Steel Grey is more saturated, cooler than Smoke Grey.
The same difference applies the other way round: Smoke Grey is more muted, 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 Smoke Grey on the colour wheel See Steel Grey on the colour wheel
All matches: Smoke Grey equivalents · Steel Grey equivalents