Moonstone Skin vs Gnome Flesh

How close are they?

ΔE 21.8, loose: different enough that you should pick on purpose. Gnome Flesh is noticeably lighter, more saturated, warmer than Moonstone Skin.

Can I use Gnome Flesh instead of Moonstone Skin?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 22). Gnome Flesh is noticeably lighter, more saturated, warmer than Moonstone Skin.

Can I use Moonstone Skin instead of Gnome Flesh?

The same difference applies the other way round: Moonstone Skin is noticeably darker, 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.