Purple Alchemy vs Volupus Pink

How close are they?

ΔE 21.1, loose: different enough that you should pick on purpose. Volupus Pink is noticeably lighter, much more saturated than Purple Alchemy.

Can I use Volupus Pink instead of Purple Alchemy?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Volupus Pink is noticeably lighter, much more saturated than Purple Alchemy.

Can I use Purple Alchemy instead of Volupus Pink?

The same difference applies the other way round: Purple Alchemy is noticeably darker, much more muted.

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.