ΔE 10.7, fair: the same colour family, but not a straight swap. Steel Grey is noticeably darker than Blue Horror.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Steel Grey is noticeably darker than Blue Horror.
The same difference applies the other way round: Blue Horror is noticeably lighter.
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 Blue Horror on the colour wheel See Steel Grey on the colour wheel
All matches: Blue Horror equivalents · Steel Grey equivalents