Purple Alchemy vs Demonic Skin

How close are they?

ΔE 25.7, loose: different enough that you should pick on purpose. Demonic Skin is a little darker, much more muted, warmer than Purple Alchemy.

Can I use Demonic Skin instead of Purple Alchemy?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 26). Demonic Skin is a little darker, much more muted, warmer than Purple Alchemy.

Can I use Purple Alchemy instead of Demonic Skin?

The same difference applies the other way round: Purple Alchemy is a little lighter, much more saturated, 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.