Faded Plum vs Light Pink

How close are they?

ΔE 27.5, loose: different enough that you should pick on purpose. Light Pink is much more saturated, warmer than Faded Plum.

Can I use Light Pink instead of Faded Plum?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 27). Light Pink is much more saturated, warmer than Faded Plum.

Can I use Faded Plum instead of Light Pink?

The same difference applies the other way round: Faded Plum is 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.