Purple Alchemy vs Fluid Pink

How close are they?

ΔE 15.8, loose: different enough that you should pick on purpose. Fluid Pink is more saturated, cooler than Purple Alchemy.

Can I use Fluid Pink instead of Purple Alchemy?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 16). Fluid Pink is more saturated, cooler than Purple Alchemy.

Can I use Purple Alchemy instead of Fluid Pink?

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