ΔE 13.4, fair: the same colour family, but not a straight swap. Fiery Red Ink is a little darker, warmer than Flesh Tearers Red. They are different kinds of paint: Citadel Flesh Tearers Red is a one-coat contrast-style paint and Nocturna Models Fiery 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.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Fiery Red Ink is a little darker, warmer than Flesh Tearers Red. They are different kinds of paint.
The same difference applies the other way round: Flesh Tearers Red is a little lighter, 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 Flesh Tearers Red on the colour wheel See Fiery Red Ink on the colour wheel
All matches: Flesh Tearers Red equivalents · Fiery Red Ink equivalents