ΔE 14.4, fair: the same colour family, but not a straight swap. Royal Purple is noticeably darker, more saturated, warmer than Steel Grey.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 14). Royal Purple is noticeably darker, more saturated, warmer than Steel Grey.
The same difference applies the other way round: Steel Grey is noticeably lighter, more muted, cooler.
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 Steel Grey on the colour wheel See Royal Purple on the colour wheel
All matches: Steel Grey equivalents · Royal Purple equivalents