ΔE 14.4, fair: the same colour family, but not a straight swap. Evil Eye Red is a little darker, cooler than Fyreslayer Flesh. They are different kinds of paint: Citadel Fyreslayer Flesh is a one-coat contrast-style paint and Two Thin Coats Evil Eye 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 14). Evil Eye Red is a little darker, cooler than Fyreslayer Flesh. They are different kinds of paint.
The same difference applies the other way round: Fyreslayer Flesh is a little lighter, warmer.
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 Fyreslayer Flesh on the colour wheel See Evil Eye Red on the colour wheel
All matches: Fyreslayer Flesh equivalents · Evil Eye Red equivalents