Light Plum vs Light Pink

How close are they?

ΔE 23.7, loose: different enough that you should pick on purpose. Light Pink is a little lighter, more muted, warmer than Light Plum.

Can I use Light Pink instead of Light Plum?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 24). Light Pink is a little lighter, more muted, warmer than Light Plum.

Can I use Light Plum instead of Light Pink?

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