Zephyr Pink vs Amethyst Purple

How close are they?

ΔE 45.5, loose: different enough that you should pick on purpose. Amethyst Purple is noticeably darker, more saturated, cooler than Zephyr Pink.

Can I use Amethyst Purple instead of Zephyr Pink?

Not as a straight swap; see the closer alternatives below. Loose match (ΔE 45). Amethyst Purple is noticeably darker, more saturated, cooler than Zephyr Pink.

Can I use Zephyr Pink instead of Amethyst Purple?

The same difference applies the other way round: Zephyr Pink is noticeably lighter, 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.