ΔE 10.7, fair: the same colour family, but not a straight swap. Ares Flesh is noticeably darker than Eldar Flesh.
Can I use Ares Flesh instead of Eldar Flesh?
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 11). Ares Flesh is noticeably darker than Eldar Flesh.
Can I use Eldar Flesh instead of Ares Flesh?
The same difference applies the other way round: Eldar Flesh is noticeably lighter.
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.