Faded Plum vs Orchid Light

How close are they?

ΔE 17.1, loose: different enough that you should pick on purpose. Orchid Light is more saturated, cooler than Faded Plum.

Can I use Orchid Light instead of Faded Plum?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 17). Orchid Light is more saturated, cooler than Faded Plum.

Can I use Faded Plum instead of Orchid Light?

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