Naphthol Red Light vs Ink Skin

How close are they?

ΔE 51.0, loose: different enough that you should pick on purpose. Ink Skin is noticeably darker, much more muted than Naphthol Red Light.

Can I use Ink Skin instead of Naphthol Red Light?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 51). Ink Skin is noticeably darker, much more muted than Naphthol Red Light.

Can I use Naphthol Red Light instead of Ink Skin?

The same difference applies the other way round: Naphthol Red Light is noticeably lighter, much more saturated.

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.