Wicked Pink vs Pastel Pink

How close are they?

ΔE 21.4, loose: different enough that you should pick on purpose. Pastel Pink is noticeably lighter, cooler than Wicked Pink.

Can I use Pastel Pink instead of Wicked Pink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 21). Pastel Pink is noticeably lighter, cooler than Wicked Pink.

Can I use Wicked Pink instead of Pastel Pink?

The same difference applies the other way round: Wicked Pink is noticeably darker, 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.