Plum vs Blueberry

How close are they?

ΔE 24.0, loose: different enough that you should pick on purpose. Blueberry is a little lighter, more saturated, cooler than Plum.

Can I use Blueberry instead of Plum?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Blueberry is a little lighter, more saturated, cooler than Plum.

Can I use Plum instead of Blueberry?

The same difference applies the other way round: Plum is a little darker, 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.