Noble Skin vs Dark Brown

How close are they?

ΔE 18.1, loose: different enough that you should pick on purpose. Dark Brown is a little darker, more saturated, warmer than Noble Skin.

Can I use Dark Brown instead of Noble Skin?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Dark Brown is a little darker, more saturated, warmer than Noble Skin.

Can I use Noble Skin instead of Dark Brown?

The same difference applies the other way round: Noble Skin is a little lighter, 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.