ΔE 10.9, fair: the same colour family, but not a straight swap. Carbon Black is more muted than Occultist Cloak. They are different kinds of paint: Army Painter Occultist Cloak is a one-coat contrast-style paint and Golden Carbon Black is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Carbon Black is more muted than Occultist Cloak. They are different kinds of paint.
The same difference applies the other way round: Occultist Cloak is 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 Occultist Cloak on the colour wheel See Carbon Black on the colour wheel
All matches: Occultist Cloak equivalents · Carbon Black equivalents