ΔE 18.1, loose: different enough that you should pick on purpose. Steel Grey is a little lighter, more muted, cooler than Spirit Blue.
Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Steel Grey is a little lighter, more muted, cooler than Spirit Blue.
The same difference applies the other way round: Spirit Blue is a little darker, 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 Spirit Blue on the colour wheel See Steel Grey on the colour wheel
All matches: Spirit Blue equivalents · Steel Grey equivalents