ΔE 11.3, fair: the same colour family, but not a straight swap. Obsidian Black is a little darker, more muted than Steel Red.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Obsidian Black is a little darker, more muted than Steel Red.
The same difference applies the other way round: Steel Red is a little lighter, more saturated.
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 Red on the colour wheel See Obsidian Black on the colour wheel
All matches: Steel Red equivalents · Obsidian Black equivalents