ΔE 14.6, fair: the same colour family, but not a straight swap. Eldritch is noticeably lighter, more saturated, cooler than Waaagh! Flesh.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 15). Eldritch is noticeably lighter, more saturated, cooler than Waaagh! Flesh.
The same difference applies the other way round: Waaagh! Flesh is noticeably darker, more muted, 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 Waaagh! Flesh on the colour wheel See Eldritch on the colour wheel
All matches: Waaagh! Flesh equivalents · Eldritch equivalents