ΔE 6.6, close: similar, with a visible difference side by side. Red Ink is warmer than Khorne Red. They are different kinds of paint: Citadel Khorne Red is an opaque base/layer paint and Reaper Red Ink is an ink, glaze or transparent paint, so they won’t behave the same on the model even where the colour is close.
Usually, if you are not matching paint already on the model. Close match (ΔE 7). Red Ink is warmer than Khorne Red. They are different kinds of paint.
The same difference applies the other way round: Khorne Red 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 Khorne Red on the colour wheel See Red Ink on the colour wheel
All matches: Khorne Red equivalents · Red Ink equivalents