ΔE 13.1, fair: the same colour family, but not a straight swap. Skrag Brown is warmer than Penetrating Red INK. They are different kinds of paint: AK Interactive Penetrating Red INK is an ink, glaze or transparent paint and Citadel Skrag Brown is an opaque base/layer 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 13). Skrag Brown is warmer than Penetrating Red INK. They are different kinds of paint.
The same difference applies the other way round: Penetrating Red INK is 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 Penetrating Red INK on the colour wheel See Skrag Brown on the colour wheel
All matches: Penetrating Red INK equivalents · Skrag Brown equivalents