ΔE 11.5, fair: the same colour family, but not a straight swap. Faded Red is a little darker, more muted than Ruby.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 12). Faded Red is a little darker, more muted than Ruby.
The same difference applies the other way round: Ruby 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 Ruby on the colour wheel See Faded Red on the colour wheel
All matches: Ruby equivalents · Faded Red equivalents