Cosmic Dust vs Sickly Skin

How close are they?

ΔE 18.4, loose: different enough that you should pick on purpose. Sickly Skin is much more muted, cooler than Cosmic Dust.

Can I use Sickly Skin instead of Cosmic Dust?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 18). Sickly Skin is much more muted, cooler than Cosmic Dust.

Can I use Cosmic Dust instead of Sickly Skin?

The same difference applies the other way round: Cosmic Dust is much 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.