Guilliman Flesh vs Nude Skin

How close are they?

ΔE 20.8, loose: different enough that you should pick on purpose. Nude Skin is more muted, cooler than Guilliman Flesh.

Can I use Nude Skin instead of Guilliman Flesh?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Nude Skin is more muted, cooler than Guilliman Flesh.

Can I use Guilliman Flesh instead of Nude Skin?

The same difference applies the other way round: Guilliman Flesh is 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.