Brown Ink vs Ink Skin

How close are they?

ΔE 18.4, loose: different enough that you should pick on purpose. Ink Skin is a little darker, more muted, cooler than Brown Ink.

Can I use Ink Skin instead of Brown Ink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Ink Skin is a little darker, more muted, cooler than Brown Ink.

Can I use Brown Ink instead of Ink Skin?

The same difference applies the other way round: Brown Ink is a little lighter, 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.