ΔE 14.7, fair: the same colour family, but not a straight swap. Brassy Brass is a little lighter, more saturated than Runefang Steel.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Brassy Brass is a little lighter, more saturated than Runefang Steel.
The same difference applies the other way round: Runefang Steel is a little darker, more muted.
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 Runefang Steel on the colour wheel See Brassy Brass on the colour wheel
All matches: Runefang Steel equivalents · Brassy Brass equivalents