ΔE 12.7, fair: the same colour family, but not a straight swap. Deck Grey is a little lighter, more muted, cooler than Eldar Flesh.
Only where an exact match doesn’t matter, such as a new unit or a highlight. Fair match (ΔE 13). Deck Grey is a little lighter, more muted, cooler than Eldar Flesh.
The same difference applies the other way round: Eldar Flesh is a little darker, more saturated, 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 Eldar Flesh on the colour wheel See Deck Grey on the colour wheel
All matches: Eldar Flesh equivalents · Deck Grey equivalents