Dark Purple vs Fluid Pink

How close are they?

ΔE 33.4, loose: different enough that you should pick on purpose. Fluid Pink is noticeably lighter, much more saturated, warmer than Dark Purple.

Can I use Fluid Pink instead of Dark Purple?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 33). Fluid Pink is noticeably lighter, much more saturated, warmer than Dark Purple.

Can I use Dark Purple instead of Fluid Pink?

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