ΔE 11.6, fair: the same colour family, but not a straight swap. Scarlett Red is a little lighter, 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 Scarlett Red 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 12). Scarlett Red is a little lighter, 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 darker, 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 Scarlett Red on the colour wheel
All matches: Flesh Tearers Red equivalents · Scarlett Red equivalents