Pharaoh Guard vs Greenskin Flesh

How close are they?

ΔE 17.3, loose: different enough that you should pick on purpose. Greenskin Flesh is more saturated, warmer than Pharaoh Guard.

Can I use Greenskin Flesh instead of Pharaoh Guard?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Greenskin Flesh is more saturated, warmer than Pharaoh Guard.

Can I use Pharaoh Guard instead of Greenskin Flesh?

The same difference applies the other way round: Pharaoh Guard is more muted, 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.